LABORATORY  MANUAL 


OF 


BITUMINOUS   MATERIALS 

FOR  THE  USE  OF 

STUDENTS  IN  HIGHWAY  ENGINEERING 


BY 

PREVOST  HUBBARD 

Chemical  Engineer 

Chief,  Division  of  Road  Material  Tests  and  Research,  Office  of  Public  Roads  and  Rural  Engi- 
neering, U.  S.  Department  of  Agriculture;  Lecturer  in  Highway  Engineering  Chemistry, 
in  the  Graduate  Course  in  Highway  Engineering,  Columbia  University,  in  the 
City  of  New  York;  Secretary,  Committee  on  Standard  Tests   for   Road 
Materials,  American  Society  for  Testing  Materials;  Associate,  American 
Society  of  Civil  Engineers;  Member,  American  Society  Municipal 
Improvements,  Association  Internationale  Permanent  des 
Congres  de  la  Route,  Association  Internationale  pour 
1'Essai  des  Materiaux 


FIRST  EDITION 
FIRST  THOUSAND 


NEW  YORK 
JOHN  WILEY  &  SONS,  INC. 

LONDON:  CHAPMAN  &  HALL,   LIMITED 

1916 


X 


Copyright,  1916,  by 
PREVOST  HUBBARD 


PUBLISHERS  PRINTING  COMPANY 
207-217  West  Twenty-fifth  Street,  New  York 


PREFACE 

DURING  the  past  five  years  a  number  of  our  leading  universi- 
ties have  inaugurated  courses  in  highway  engineering  in  which 
laboratory  instruction  is  given  in  the  testing  of  bituminous 
materials.  A  general  tendency  appears  to  exist  upon  the  part 
of  many  other  educational  institutions  to  develop  the  same  line 
of  activity  because  of  the  desire  of  highway  engineers  through- 
out the  country  to  familiarize  themselves  with  these  materials. 

While  numerous  technical  and  scientific  papers  have  been 
published  upon  this  subject  in  more  or  less  detail,  no  attempt 
has  as  yet  been  made  to  furnish  the  student  in  highway  engi- 
neering with  a  complete  laboratory  manual.  As  the  result  of 
his  experience  since  1912  in  laboratory  instruction  in  bitumi- 
nous materials  given  in  the  Graduate  Course  in  Highway  En- 
gineering at  Columbia  University,  the  author  has  endeavored  to 
prepare  a  manual  which  may  perhaps  fill  a  want  both  upon  the 
part  of  instructors  and  students  and  also  those  highway  engi- 
neers in  charge  of  State,  county,  or  municipal  work  who  have, 
or  expect  to  have,  a  laboratory  at  their  disposal.  The  author 
fully  realizes  that  no  first  attempt  along  this  line  is  apt  to  meet 
the  many-sided  demand,  and  will  welcome  criticisms  and  sug- 
gestions from  those  who  are  sufficiently  interested  to  make 
them. 

In  the  preparation  of  this  manual  no  attempt  has  been 
made  to  trace  down  the  obscure  origin  of  many  methods  of 
testing  which  are  described.  The  author  has,  however,  en- 
deavored to  give  credit  in  all  cases  where  the  originator  is 
known,  and  if  by  chance  any  are  unintentionally  slighted,  he 
takes  this  occasion  to  offer  his  sincere  apologies.  Many  of  the 
methods  described  are  taken  practically  verbatim  from  U.  S. 
Department  of  Agriculture  Bulletin  No.  314,  by  Hubbard  and 
Reeve.  Other  publications  which  have  been  drawn  upon  for 

ill 


357303 


IV  PREFACE 

original  descriptions  are  "The  Modern  Asphalt  Pavement,"  by 
Clifford  Richardson;  " Methods  for  Testing  Coal  Tars  and 
Refined  Tars  and  Oils  and  Pitches  Derived  Therefrom/'  by  S.  R. 
Church,  and  The  Proceedings  of  The  American  Society  for 
Testing  Materials,  and  The  American  Society  of  Civil  Engineers. 
For  many  helpful  suggestions  relative  to  the  arrangement  and 
development  of  the  subject-matter  of  this  book  the  author 
wishes  to  express  his  indebtedness  to  Professor  Arthur  H. 
Blanchard. 

PREVOST  HUBBARD. 
WASHINGTON,  D.  C. 
July  15,  1916. 


INTRODUCTION 

THIS  manual  is  primarily  intended  as  a  laboratory  guide 
for  the  student  of  highway  engineering  and  not  as  a  treatise 
upon  methods  of  analyses  and  tests  of  bituminous  materials. 
Its  object  is  to  describe  methods  in  sufficient  detail  to  enable 
the  student  to  perform  the  more  common  and  widely  used  tests 
with  a  reasonable  degree  of  accuracy,  provided  his  work  is  care- 
fully conducted  and  he  is  supplied  with  the  necessary  labora- 
tory equipment.  Certain  tests  not  in  general  use  have  been  en- 
tirely eliminated  from  consideration,  while  others  which  have 
been  included,  together  with  those  of  minor  importance,  are 
shown  in  fine  print  to  separate  them  from  the  more  common 
and  more  important  methods. 

The  arrangement  of  subject-matter  in  the  following  pages 
is  designed  to  develop  not  only  the  abstract  technique  of  the 
bituminous  material  laboratory,  but  also  to  deal  with  the  inter- 
pretation of  results  of  tests  in  connection  with  the  identifica- 
tion, suitability  for  specific  purposes,  and  control  of  uniformity 
of  materials  tested.  The  treatment  is  intended  to  be  as  brief 
as  lucidity  permits.  Certain  fundamentals  not  strictly  a  part 
of  laboratory  work  have,  however,  been  included  in  Part  I  for 
a  guide  to  students  not  well  versed  in  the  nomenclature,  classi- 
fication, and  uses  of  bituminous  materials. 

In  the  matter  of  interpreting  the  results  of  tests  it  should 
be  realized  that  it  is  impossible  to  take  into  account  all  con- 
ceivable combinations  of  conditions.  Moreover,  our  knowledge 
of  the  subject  is  yet  far  from  being  perfect,  and  many  conflict- 
ing ideas  are  held  by  different  highway  engineers  and  chemists 
regarding  certain  matters.  To  some  extent,  therefore,  interpre- 
tation of  test  results  should  be  considered  as  opinions  based 
upon  personal  observations  at  the  time  such  opinions  are  ex- 
pressed. As  new  facts  are  developed  and  observations  are 


VI  INTRODUCTION 

extended,  these  opinions  become  subject  to  modification  or 
entire  change.  If  the  matter  is  viewed  in  this  light  it  becomes 
apparent  that  at  the  present  time  any  dissertation  upon  inter- 
pretation of  results  should  be  considered  more  as  a  guide  than 
as  a  collection  of  definite  rules  or  laws  which  are  not  subject 
to  modification. 

There  are  a  number  of  important  considerations  which  have 
to  be  reckoned  as  variables  affecting  conclusions  drawn  from  a 
comparison  of  laboratory  tests  with  service  results.  The  first 
of  these  is  variations  in  test  results  from  different  laboratories, 
due  to  lack  of  standardization  of  methods,  and  also  to  careless 
operation.  Too  careful  attention  cannot  be  paid  to  even  the 
apparently  minor  details  of  a  method  if  consistent  results  are 
to  be  expected.  The  second  point  is,  what  constitutes  satis- 
factory service  results?  That  which  is  quite  satisfactory  to  one 
engineer  in  view  of  past  experiences  may  prove  far  from  satis- 
factory to  another  of  a  more  exacting  nature.  It  is  of  course 
highly  desirable  to  approach  the  ideal  as  nearly  as  possible,  but 
in  attempting  this  the  question  of  what  is  practical  under  ordi- 
nary conditions  must  not  be  disregarded. 

Quite  frequently  unsatisfactory  service  results  are  obtained 
from  the  improper  or  careless  use  of  first-class  materials.  In 
such  cases,  unless  the  true  cause  of  failure  is  plainly  apparent, 
there  is  a  natural  tendency  to  place  the  blame  upon  the  char- 
acter of  the  material  used.  This  is  apt  to  lead  to  much  con- 
fusion in  interpreting  the  results  of  laboratory  tests. 

In  the  case  of  bituminous  highways  it  should  be  remembered 
that  the  bituminous  material  constitutes  but  a  relatively  small 
proportion  of  the  road  structure,  and  that  failure  is  quite  as 
likely  to  be  due  to  the  use  of  inferior  products  other  than  the 
bituminous  material.  The  quality  of  such  materials  as  broken 
stone,  gravel,  sand,  filler,  wood,  etc.,  is  of  as  much  importance 
from  the  standpoint  of  success  or  failure  as  of  the  bitumen. 
Moreover,  some  types  and  grades  of  bituminous  materials  which 
will  prove  satisfactory  with  one  type  of  aggregate  will  not  prove 
as  satisfactory  with  another  type  of  an  apparently  equivalent 
grading. 


INTRODUCTION  Vll 

Another  frequent  cause  of  unsatisfactory  service  results  is 
faulty  construction.  Thus,  poor  drainage  may  cause  rapid  dis- 
integration and  failure  of  a  carefully  constructed  wearing  course 
laid  with  good  material.  A  rough,  uneven,  or  poorly  compacted 
foundation  will  almost  invariably  produce  an  unsatisfactory 
surface.  Last  but  not  least,  the  selection  of  the  wrong  type  of 
pavement  to  meet  existing  traffic  and  other  local  conditions 
may  result  in  failure  through  no  inherent  fault  of  the  materials 
themselves  except  that  they  were  not  of  the  proper  grade  or 
character  to  meet  the  given  conditions. 

The  laboratory  may  be  made  a  valuable  asset  in  highway 
engineering,  but  unless  the  engineer  understands  the  principles 
involved  in  the  analyses  of  bituminous  materials  and  thoroughly 
appreciates  the  necessity  of  correlating  test  values  with  service 
results,  it  may  prove  to  be  a  handicap,  particularly  in  the 
matter  of  formulating  specifications.  There  should  be  close 
cooperation  and  frequent  interchange  of  ideas  between  the  high- 
way engineer  and  the  testing  engineer  or  chemist  if  the  maxi- 
mum value  of  the  laboratory  is  to  be  developed. 


TABLE  OF  CONTENTS 


PAGE 
INTRODUCTION    .  .     .  v 


PART  I— GENERAL 

Use  of  the  Manual  ...           I 

Important  Definitions 2 

Definitions  of  Materials 2 

Definitions  Relating  to  Tests 5 

Definitions  Relating  to  Use 6 

Types  of  Bituminous  Materials 7 

Classification  of  Crude  Bituminous  Materials 9 

Refining  Processes 10 

Classification  of  Bituminous  Road  and  Paving  Materials 15 

Laboratory  Sampling,  Preparation,  and  Manipulation 19 

Laboratory  Reports  and  Records 22 


PART  II— METHODS  OF  TESTING 

Density  Tests 29 

Specific  Gravity 29 

Basis  of  Determination 29 

Hydrometer  Method 30 

Westphal  Balance  Method 32 

Sprengel  or  Nicol  Tube  Method 33 

Pycnometer  Method 34 

Displacement  Method 36 

Method  for  Coarse  Mineral  Aggregates 37 

Method  for  Fine  Mineral  Aggregates 38 

Value  of  Specific  Gravity  Determination 38 

Coefficient  of  Expansion 40 

Basis  of  Determination 40 

Specific  Gravity  Method 41 

Value  of  Determination 42 

Consistency  Tests 43 

Viscosity 43 

Value  of  Determination 45 

ix 


X  TABLE    OF    CONTENTS 

Consistency  Tests  PAGE 

Float  Test 47 

Value  of  Test 49 

Penetration  Test 50 

Value  of  Test .  .  54 

Melting  or  Softening  Point  Tests 56 

Cube  Method 56 

Ring  and  Ball  Method 58 

Value  of  Melting  Point  Test 60 

Ductility 61 

Value  of  Test 64 

Heat  Tests 65 

Flash  and  Burning  Points *  ...  65 

Open  Cup  Method 65 

Closed  Cup  Method 66 

Value  of  Flash  and  Burning  Point  Determinations  ....  68 

Volatilization  Test 69 

Old  Method 69 

New  Method 71 

Conditions  Affecting  the  Volatilization  Test 73 

Value  of  the  Volatilization  Test 74 

Dehydration — Determination  of  Water       ........  75 

Value  of  Test .  . 76 

Distillation  Tests 76 

Flask  Method  .......  v  ./. 76 

Retort  Method 80 

Value  of  Distillation  Test 83 

Solubility  Tests  on  Other  than  Bituminous  Aggregates 84 

Total  Bitumen 84 

Rapid  Method 84 

Long  Method ".*.'.'.'..  88 

Value  of  Total  Bitumen  Determination  .......  89 

Asphaltenes  or  Bitumen  Insoluble  in  Paraffin  Naphtha  ....  90 

Value  of  Determination 92 

Carbenes  or  Bitumen  Insoluble  in  Carbon  Tetrachloride  ...  93 

Value  of  Determination 94 

Dimethyl  Sulphate  Test 95 

Value  of  Test  .  .  .  .  '.  . 96 

Miscellaneous  Tests 96 

Fixed  Carbon  and  Ash  . .  96 

Value  of  Determination 99 

Paraffin  Scale 100 

Value  of  Determination 103 

Special  Tests  for  Emulsions 103 

Fatty  and  Resin  Acids 104 

Water 104 

Ammonia 104 

Ash  104 


TABLE    OF    CONTENTS  XI 


Miscellaneous  Tests  PAGE 

Total  Bitumen 104 

Solubility  in  Benzol  or  Chloroform — Hot  Extraction        .      .      .      .  104 

Special  Tests  for  Creosoting  Oils 105 

Tar  Acids 106 

Dry  Naphthalene      .  t 106 

Sulphonation  Test 107 

Extraction  of  Bituminous  Aggregates  and  Recovery  of  Bitumen  and 

Aggregate 108 

Centrifugal  Extraction 108 

Hot  Extraction in 

Recovery  of  Bitumen 113 

Filtration  Extraction 114 

Grading  of  Mineral  Aggregates 115 

Mechanical  Analysis  of  Sand  or  Other  Fine  Material     .      .      .  117 

Mechanical  Analysis  of  Broken  Stone  or  Slag 118 

Mechanical  Analysis  of  Mixed  Fine  and  Coarse  Aggregate       .  118 

Value  of  Tests  for  Bituminous  Aggregates 119 

PART  III— CHARACTERISTICS  OF  THE  MORE  IMPORTANT  BITU- 
MINOUS MATERIALS 

Fluid  Petroleum  Products  and  Emulsions     .      .     .      .     .     .     *     .     .  121 

Ordinary  Tests  .  .  -.  .  ...  .  .  .  .  ...  .  .  121 

Analyses  of  Fluid  Petroleum  Products 123 

Interpretation  of  Results        .      .      .      .      .      .     .    *.      ,  *  .      .      .  122 

Analyses  of  Emulsifying  Oils  and  Emulsions  ...,*...  128 

Interpretation  of  Results  ....  * 127 

Semisolid  and  Solid  Petroleum  and  Asphalt  Products 129 

Ordinary  Tests 129 

Analyses  of  Oil  Asphalts  and  Fillers *..  .131 

Interpretation  of  Results 130 

Analyses  of  Native  Asphalts  and  Asphalt  Cements 134 

Interpretation  of  Results .  .  .  .  .  133 

Refined  Tars  and  Tar  Pitches . 137 

Ordinary  Tests 139 

Analyses  of  Refined  Tars 141 

Interpretation  of  Results 140 

Creosoting  Oils  or  Wood  Preservatives  .  .'.  .  .  ..  .  .  .  145 

Ordinary  Tests  .....i 146 

Specification  Limits  for  Wood  Preservatives 146 

Interpretation  of  Tests  .  ..  . .  .  .,  .  ..  .  .  .  147 

Bituminous  Aggregates 147 

Rational  Per  Cent  of  Bitumen  .  .  .  ...  .  .  .  *  .  148 

Density  and  Voids • 149 

Analyses  of  Bituminous  Aggregates       .      .      .     .      .     .     .      .      .  152 

Interpretation  of  Results .  .  151 


LABORATORY  MANUAL 

OF 

BITUMINOUS  MATERIALS 

FOR  USE  OF  STUDENTS  IN  HIGHWAY  ENGINEERING 

PART  I— GENERAL 

USE  OF  THE  MANUAL 

Before  attempting  work  in  the  bituminous  material  lab- 
oratory, the  student  who  uses  this  manual  should  thoroughly 
familiarize  himself  with  the  subject-matter  of  Part  I.  When 
handling  an  unknown  material  he  should  first  identify  it  as  to 
type  and  grade.  In  most  cases  the  general  appearance  of  the 
material,  together  with  its  odor  when  warm  and  its  apparent 
consistency,  will  enable  him  to  do  this.  If  still  in  doubt,  a  deter- 
mination of  specific  gravity  and  a  consistency  test  as  described 
in  Part  II  may  be  made.  The  interpretation  of  results  under 
the  specific  gravity  test  may  then  be  used  to  identify  roughly  the 
material  under  one  of  the  following  classes: 

1.  Fluid  Petroleum  Products  and  Emulsions. 

2.  Semisolid  and  Solid  Petroleum  and  Asphalt  Products. 

3.  Refined  Tars  and  Tar  Pitches. 

4.  Creosoting  Oils. 

5.  Bituminous  Aggregates. 

When  this  is  done,  the  student  should  turn  to  Part  III. 
Under  the  proper  classification  he  will  find  a  list  of  the  ordi- 
nary tests  to  make  upon  the  material,  together  with  comments 
upon  the  interpretation  of  results.  These  tests  should  then  be 
made  in  accordance  with  methods  described  in  Part  II.  The 
blank  pages  in  Part  III  may  be  used  to  insert  analyses  of 
particular  interest  and  additional  facts  which  may  develop 
relative  to  the  significance  of  tests.  After  the  student  has 
thoroughly  familiarized  himself  with  the  various  types  and 

1 


2  IMPORTANT    DEFINITIONS 

grades  of  bituminous  materials,  he  will  be  prepared  for  more 
advanced  work  in  connection  with  the  specification  of  materials. 
It  should  be  borne  in  mind,  however,  that  the  matter  of 
preparing '  specifications  should  not  be  attempted  until  the 
student  has  had  considerable  field  experience  or  has  had  an 
opportunity  to  observe  the  behavior  of  the  various  materials 
under  known  service  conditions. 

IMPORTANT  DEFINITIONS 

The  following  definitions  are  considered  important  in  con- 
nection with  the  use  of  this  manual.  For  this  purpose  the 
terms  are  arranged  in  groups,  according  to  logical  sequence 
rather  than  alphabetically.  Those  marked  with  an  *  have  been 
adopted  as  standard  by  The  American  Society  for  Testing 
Materials;  those  marked  with  a  f  have  been  recommended 
to  The  American  Society  for  Testing  Materials  by  its  Com- 
mittee on  Standard  Tests  for  Road  Materials,  and  those  marked 
with  a  {  have  been  proposed  to  The  American  Society  of  Civil 
Engineers  by  The  Special  Committee  on  Materials  for  Road 
Construction  and  on  Standards  for  Their  Tests  and  Use.  In 
certain  instances  comments  have  been  added  by  the  author 
and  definitions  have  been  included  which  have  not  been  recom- 
mended to  or  adopted  by  any  technical  society. 

DEFINITIONS   OF  MATERIALS 

Bitumens  *$ — Mixtures  of  native  or  pyrogenous  hydro- 
carbons and  their  non-metallic  derivatives,  which  may  be  gases, 
liquids,  viscous  liquids,  or  solids,  and  which  are  soluble  in  car- 
bon disulphide.  Note:  Broadly  this  term  includes  petroleums, 
asphalts,  and  tars  which  may  or  may  not  contain  impurities 
insoluble  in  carbon  disulphide.  From  a  rigid  interpretation  of 
the  definition  such  substances  should  be  more  properly  termed 
bituminous  materials  unless  free  from  impurities  which  are  not 
bitumen. 

Bituminous* — Containing  bitumen  or  constituting  the  source 
of  bitumen.  Note:  (i)  As  bituminous  aggregate.  (2)  As  bitu- 
minous coal. 


DEFINITIONS    OF    MATERIALS  6 

Bituminous  Material.% — Material  containing  bitumen  as  an 
essential  constituent. 

Solid  Bituminous  Materials*  % — Those  having  a  penetration 
at  25°  C.  (77°  F.),  under  a  load  of  100  grams  applied  for  5  sec- 
onds, of  not  more  than  10. 

Liquid  Bituminous  Materials .*  { — Those  having  a  penetra- 
tion at  25°  C.  (77°  F.),  under  a  load  of  50  grams  applied  for 
i  second,  of  more  than  350. 

Semisolid  Bituminous  Materials*  % — Those  having  a  pene- 
tration at  25°  C.  (77°  F.),  under  a  load  of  100  grams  applied 
for  5  seconds,  of  more  than  10,  and  a  penetration  at  25°  C. 
(77°  F.),  under  a  load  of  50  grams  applied  for  i  second,  of  not 
more  than  350. 

Bituminous  Aggregate. — A  mineral  or  other  aggregate  con- 
taining bitumen  as  a  cementing  medium. 

Bituminous  Mastic. — A  bituminous  aggregate,  the  mineral 
portion  of  which  consists  of  very  fine  particles. 

Bituminous  Rock. — Rock  naturally  impregnated  with  petro- 
leum or  asphalt. 

Bituminous  Emulsion.^ — A  liquid  mixture  in  which  minute 
globules  of  bitumen  are  held  in  suspension  in  water  or  a  watery 
solution. 

Petr oleum. \ — Liquid  bitumen  occurring  as  such  in  nature. 

Topped  Petroleum.^ — Petroleum  deprived  of  its  more  vola- 
tile constituents. 

Residual  Petroleum. — A  liquid  residue  obtained  by  distilling 
petroleum  to  a  point  beyond  which  water  and  oils  accompany- 
ing the  elimination  of  water  are  removed. 

Blown  Petroleums*  J — Semisolid  or  solid  products  produced 
primarily  by  the  action  of  air  upon  liquid  native  bitumens  which 
are  heated  during  the  blowing  process. 

Asphaltic  Petroleum. — Petroleum  which,  upon  evaporation  or 
fractional  distillation  without  blowing,  will  yield  an  asphalt 
cement. 

Paraffin  Petroleum. — Petroleum  which,  upon  evaporation  or 
fractional  distillation,  will  yield  a  greasy  residue  containing  an 
appreciable  quantity  of  paraffin  hydrocarbons. 


4  DEFINITIONS    OF    MATERIALS 

Malthas. — Very  viscous  petroleums. 

Asphalts*  J — Solid  or  semisolid  native  bitumens,  solid  or 
semisolid  bitumens  obtained  by  refining  petroleum,  or  solid  or 
semisolid  bitumens  which  are  combinations  of  the  bitumens 
mentioned  with  petroleums  or  derivatives  thereof  which  melt 
upon  the  application  of  heat  and  which  consist  of  a  mixture 
of  hydrocarbons  and  their  derivatives  of  complex  structure, 
largely  cyclic  and  bridge  compounds. 

Native  Asphalt* — Asphalt  occurring  as  such  in  nature. 

Refined  Asphalt. — Asphalt  which  has  been  subjected  to 
a  refining  process  but  which  is  ordinarily  too  hard  for  use  in 
the  manufacture  of  bituminous  pavements  until  softened  by 
combining  it  with  a  flux.  Note:  Commonly  designated  in  paving 
work  as  "R.  A." 

Oil  Asphalt. — Asphalt  manufactured  directly  from  petroleum. 

Asphalt  Cement* — A  fluxed  or  unfluxed  asphalt  especially 
prepared  as  to  quality  and  consistency  for  direct  use  in  the 
manufacture  of  bituminous  pavements,  and  having  a  penetra- 
tion at  25°  C.  (77°  F.),  of  between  5  and  250,  under  a  load  of 
100  grams  applied  for  5  seconds.  Note:  Commonly  designated 
in  paving  work  as  "A.  C." 

Rock  Asphalt. \ — Sandstone  or  limestone  naturally  impreg- 
nated with  asphalt. 

Asphalt  Block. — Paving  block  composed  of  compressed 
asphaltic  concrete. 

Tar s*  \ — Bitumens  which  yield  pitches  upon  fractional  dis- 
tillation and  which  are  produced  as  distillates  by  the  destructive 
distillation  of  bitumens,  pyrobitumens,  or  other  organic  materials. 

Dehydrated  Tars*  \— Tars  from  which  all  water  has  been 
removed. 

Refined  Tar.*% — Tar  freed  from  water  by  evaporation  or  dis- 
tillation until  the  residue  is  of  desired  consistency,  or  a  product 
produced  by  fluxing  tar  residuum  with  tar  distillate. 

Coal  Tar*  % — The  mixture  of  hydrocarbon  distillates,  mostly 
unsaturated  ring  compounds,  produced  in  the  destructive  dis- 
tillation of  coal. 

Gas-House  Coal    Tar*% — Coal  tar  produced  in  gas-house 


DEFINITIONS    RELATING   TO    TESTS  5 

retorts  in  the  manufacture  of  illuminating  gas  from  bituminous 
coal. 

Coke-Oven  Tar*  { — Coal  tar  produced  in  by-product  coke 
ovens  in  the  manufacture  of  coke  from  bituminous  coal. 

Oil-Gas  Tars* — Tars  produced  by  cracking  oil  vapors  at 
high  temperatures  in  the  manufacture  of  oil  gas. 

Water-Gas  Tars* — Tars  produced  by  cracking  oil  vapors  at 
high  temperatures  in  the  manufacture  of  carburetted  water  gas. 

Flux*  | — Bitumens,  generally  liquid,  used  in  combination 
with  harder  bitumens  for  the  purpose  of  softening  the  latter. 

Cut-Back  Products* — Petroleum  or  tar  residuums  which 
have  been  fluxed  with  distillates. 

Pitches*  { — Solid  residues  produced  in  the  evaporation  or 
distillation  of  bitumens,  the  term  being  usually  applied  to  residues 
obtained  from  tars. 

Straight-Run  Pitch* — A  pitch  run  to  the  consistency  desired, 
in  the  initial  process  of  distillation,  without  subsequent  fluxing. 

Dead  Oils*  % — Oils  with  a  density  greater  than  water  which 
are  distilled  from  tars. 

Creosoting  Oil. — Tar  distillates,  tars  and  mixtures  of  tars  with 
tar  distillates  which  are  used  by  a  process  of  impregnation  in  the 
preservation  of  wood.  Note :  This  term  was  originally  confined 
to  the  heavier  coal-tar  distillates  carrying  a  large  proportion 
of  the  cresols  which  were  present  in  the  tar  before  distillation. 

DEFINITIONS  RELATING  TO  TESTS 

Total  Bitumen. — That  portion  of  bituminous  materials,  con- 
sisting of  hydrocarbons  and  their  non-metallic  derivatives,  which 
is  completely  soluble  in  carbon  disulphide. 

Asphaltenes*  \ — The  components  of  the  bitumen  in  petro- 
leums, petroleum  products,  malthas,  asphalt  cements,  and  solid 
native  bitumens  which  are  soluble  in  carbon  disulphide  but 
insoluble  in  paraffin  naphthas.  Note:  The  paraffin  naphtha 
most  generally  used  for  determining  the  percentage  of  asphal- 
tenes  has  a  gravity  of  from  86°  to  88°  Baume,  with  at  least 
85%  distilling  between  35°  and  65°  C. 

Carbenes*l — The  components  of  the  bitumen  in  petroleums, 


6  DEFINITIONS    RELATING    TO    USE 

petroleum  products,  malthas,  asphalt  cements,  and  solid  native 
bitumens  which  are  soluble  in  carbon  disulphide  but  insoluble 
in  carbon  tetrachloride. 

Naphthalene. — A  solid  crystalline  highly  volatile  hydrocar- 
bon occurring  principally  in  tars,  and  having  the  chemical 
formula  CioH8. 

Free  Carbon  in  Tars*% — Organic  matter  which  is  insoluble 
in  carbon  disulphide. 

Fixed  Carbon*  { — The  organic  matter  of  the  residual  coke 
obtained  upon  burning  hydrocarbon  products  in  a  covered  ves- 
sel in  the  absence  of  free  oxygen. 

Normal  Temperature*  J — As  applied  to  laboratory  observa- 
tions of  the  physical  characteristics  of  bituminous  materials,  is 
25°  C.  (77°  F.).  Note:  In  the  calibration  of  the  volume  of  con- 
tainers and  the  gauging  of  their  contents,  15.5°  C.  (60°  F.)  is 
customarily  considered  as  normal  temperature. 

Consistency*  J — The  degree  of  solidity  or  fluidity  of  bitu- 
minous materials. 

Viscosity. \ — The  measure  of  the  resistance  to  flow  of  a 
bituminous  material,  usually  stated  as  the  time  of  flow  of  a 
given  amount  of  the  material  through  a  given  orifice. 

Penetration.^ — The  consistency  of  a  bituminous  material 
expressed  as  the  distance  that  a  standard  needle  vertically  pene- 
trates a  sample  of  the  material  under  known  conditions  of  load- 
ing, time,  and  temperature.  When  the  conditions  of  test  are 
not  specifically  mentioned,  the  load,  time,  and  temperature  are 
understood  to  be  100  grams,  5  seconds,  25°  C.  (77°  F.),  and 
the  units  of  penetration  to  indicate  hundredths  of  a  centimeter. 

DEFINITIONS  RELATING  TO  USE 

Dust  Preventive.  Material  applied  to  a  road  surface  for 
preventing  the  formation  or  dispersion  under  traffic  of  dust. 

Bituminous  Surf  ace. % — A  superficial  coat  of  bituminous  ma- 
terial with  or  without  the  addition  of  stone  or  slag  chips,  gravel, 
sand,  or  material  of  similar  character. 

Carpeting  Medium. — Bituminous  material  applied  to  a  road 
surface  primarily  for  protecting  the  road  proper  from  the  wear 


TYPES    OF    BITUMINOUS    MATERIALS  7 

and  tear  of  traffic  through  the  formation  of  a  mat  or  carpet 
covering. 

Carpet.% — A  bituminous  surface  of  appreciable  thickness, 
generally  formed  on  top  of  a  road  or  pavement  by  the  appli- 
cation of  one  or  more  coats  of  bituminous  material  with  gravel, 
sand,  or  stone  chips  added. 

Seal-Coating  Material. — Bituminous  material  applied  to  the 
surface  of  a  bituminous  road  primarily  for  the  purpose  of  filling 
surface  voids  and  producing  a  smooth,  uniform  wearing  surface. 

Bituminous  Cement. — Bituminous  material  introduced  into 
the  road  structure  primarily  for  the  purpose  of  cementing  to- 
gether and  holding  in  place  the  fragments  of  mineral  aggregate. 

Bituminous  Macadam  Pavement. — One  having  a  wearing 
course  of  macadam  with  the  interstices  filled  with  a  bituminous 
binder  applied  by  the  penetration  or  pouring  method. 

Bituminous  Concrete  Pavement.^. — One  composed  of  stone, 
gravel,  sand,  shell,  or  slag,  or  combinations  thereof,  and  bitu- 
minous materials  incorporated  together  by  mixing  methods. 
Note:  This  definition  includes  sheet-asphalt  pavements  which 
are  not  ordinarily  considered  as  bituminous  concrete. 

Sheet- Asphalt  Pavement.* — One  having  a  wearing  course 
composed  of  asphalt  cement  and  sand  of  predetermined  grad- 
ing, with  or  without  the  addition  of  fine  material,  incorporated 
together  by  mixing  methods. 

Sheet-Asphalt  Topping. — The  bituminous  aggregate  used  in  the 
construction  of  the  wearing  course  of  a  sheet-asphalt  pavement. 

Binder  Course. — A  rather  coarse  bituminous  aggregate  con- 
taining a  relatively  small  percentage  of  bitumen,  commonly 
used  as  an  intermediate  course  between  the  foundation  and 
wearing  course  of  a  sheet-asphalt  pavement. 

Bituminous  Filler. — Bituminous  material  primarily  used  for 
filling  the  joints  in  brick,  block,  concrete,  or  other  pavements. 

TYPES  OF  BITUMINOUS  MATERIALS 

There  are  a  great  many  types  of  bituminous  materials,  but 
only  a  comparatively  few  are  of  direct  interest  to  the  highway 
engineer  at  present.  In  classifying  these  types  it  is  most  con- 


8  TYPES    OF    BITUMINOUS    MATERIALS 

venient  to  consider  the  crude  materials.  Of  these  there  are 
two  main  groups,  native  and  artificial  or  pyrogenous. 

The  native  bituminous  materials  may  be  either  liquid,  semi- 
solid,  or  solid.  The  liquids  are  known  as  petroleums  and  malthas 
and  run  from  thin  fluids  to  those  which  are  very  viscous  and 
almost  semisolid.  There  are  two  well-defined  classes  of  petro- 
leums— paraffin  and  asphaltic.  There  is  also  an  intermediate 
class  commonly  termed  semi-asphaltic.  The  semisolid  and  solid 
native  bituminous  materials  of  direct  interest  divide  themselves 
into  two  classes,  asphalts  and  rock  asphalts.  Most  of  the  na- 
tive bituminous  materials  from  a  given  locality  possess  certain 
chemical  or  physical  properties  which  serve  to  identify  them 
and  to  distinguish  them  from  materials  obtained  from  other 
localities.  They  are  therefore  most  conveniently  classified  ac- 
cording to  the  location  from  which  they  are  obtained.  We  thus 
speak  of  California,  Texas,  and  Mexican  petroleum,  Trinidad 
and  Bermudez  asphalt,  Kentucky  and  Sicilian  rock  asphalt,  etc. 

The  crude  artificial  or  pyrogenous  bituminous  materials 
are  fluid  products  known  as  tars.  Like  the  petroleums,  they 
run  from  thin  liquids  to  those  which  are  very  viscous.  There 
are  two  classes  of  tars  of  direct  interest  to  the  highway  engineer, 
coal  tars  and  water-gas  tars.  The  former,  as  their  name  implies, 
are  derived  from  bituminous  coal  by  a  process  of  destructive  dis- 
tillation. Water-gas  tars  are,  however,  derived  from  petroleum  or 
petroleum  products  by  a  cracking  process  in  the  manufacture  of 
carburetted  water  gas.  As  practically  all  crude  tars  are  by-prod- 
ucts, they  may  be  further  classified  according  to  the  process  by 
which  they  are  obtained  and  the  type  of  apparatus  involved  in 
the  process.  We  thus  have  under  coal  tars  two  groups:  (i)  gas- 
house  and  (2)  coke-oven;  and  under  the  first  group  horizontal 
retort,  inclined  retort,  and  vertical  retort  tars.  This  method  of 
classification  is  particularly  convenient  as  a  means  of  identifi- 
cation, as  the  process  of  manufacture  and  type  of  apparatus 
influence  the  character  of  the  tar  much  more  than  does  the 
character  of  the  original  material  which  is  destructively  distilled 
or  cracked  to  produce  them. 

In  most  cases  crude  bituminous  materials  are  much  easier 


CLASSIFICATION    OF    CRUDE    BITUMINOUS    MATERIALS  9 

to  identify  than  are  the  products  refined  or  manufactured 
from  them  for  use  in  highway  work.  This  is  due  to  the  fact 
that  many  refined  products  consist  of  a  blend  or  combination 
of  two  or  more  types.  Certain  distinguishing  characteristics  of 
the  original  crude  materials  may,  however,  often  be  discovered 
in  a  refined  product  and  thus  serve  to  identify  at  least  its  pre- 
dominating source.  A  knowledge  of  the  characteristics  of  crude 
bituminous  materials  is  therefore  of  considerable  value  in  the 
interpretation  of  the  results  of  tests  made  upon  the  refined 
products  directly  used  in  highway  engineering. 

The  following  outline,  while  far  from  complete,  will  serve 
as  a  general  classification  of  crude  bituminous  materials  of  most 
interest  to  the  highway  engineer. 

CLASSIFICATION  OF  CRUDE  BITUMINOUS 

MATERIALS 
I.    NATIVE. 

a.  Fluids. 

1.  Paraffin  Petroleums: 

Pennsylvania. 
Ohio-Indiana  or  Lima. 

2.  Semi-asphaltic  and  Asphaltic  Petroleums: 

Mid-Continent. 

Texas. 

Southern  Illinois. 

California. 

Mexican. 

Trinidad. 

b.  Semisolids  and  Solids. 

1.  Asphalts: 

Trinidad. 

Bermudez. 

Cuban. 

Gilsonites. 

Grahamites. 

2.  Rock  Asphalts: 

Kentucky. 


10  REFINING    PROCESSES 

Uvalde. 

Sicilian — Ragusa. 
Val  de  Travers. 
Seyssel. 
II.    PYROGENOUS. 

a.  Produced  from  Coal. 

1.  Gas-House  Coal  Tars: 

Horizontal  Retort. 
Inclined  Retort. 
Vertical  Retort. 

2.  Coke-Oven  Tars: 

Koppers. 
Semet-Solvay. 
United  Otto. 
Otto-Hoffman. 
Rothburg. 

b.  Produced  from  Petroleum. 

1.  Oil-Gas  Tars. 

2.  Water-Gas  Tars. 


REFINING  PROCESSES 

The  ordinary  refining  processes  employed  in  the  manufacture 
of  bituminous  road  and  paving  materials  may  be  classified  as 
follows: 

I.    Removal  of  Non-bituminous  Impurities: 

a.  Sedimentation. 

b.  Dehydration. 
II.    Distillation: 

a.  Fractional  Distillation. 

b.  Cracking. 

c.  Destructive  Distillation. 

III.  Oxidation  or  Blowing. 

IV.  Fluxing: 

a.  Fluxing  with  Residuals. 

b.  Fluxing  with  Distillates — Cutting-Back. 

c.  Emulsification. 


REFINING    PROCESSES  11 

Sedimentation. — Water  is  the  most  common  impurity  in  both 
fluid  and  solid  crude  bituminous  materials.  Mineral  matter, 
vegetable  matter,  and  occluded  gases  are  other  natural  occur- 
ring impurities.  As  most  of  these  impurities  are  insoluble  in 
the  bitumen  proper,  and  as  they  differ  from  the  bitumen  in 
specific  gravity,  they  may  be  removed  wholly  or  in  part  by 
the  process  of  sedimentation  or  separation  by  gravity.  In  the 
more  fluid  bituminous  materials,  natural  sedimentation  occurs 
during  storage  in  large  tanks.  In  the  case  of  crude  petroleums, 
the  water  and  mineral  matter  settle  to  the  bottom,  leaving 
practically  pure  bitumen  above.  In  the  case  of  tars  which  are 
heavier  than  water,  the  water  rises  to  the  top,  leaving  the  tar, 
together  with  certain  impurities,  such  as  free  carbon,  which  will 
not  separate  by  sedimentation,  in  the  bottom  of  the  tank.  Very 
viscous  fluids  persistently  retain  a  small  amount  of  water,  and 
the  separation  of  this  water  may  often  be  expedited  by  equip- 
ping the  storage  tank  with  steam  coils,  by  which  means  the 
temperature  of  the  bitiirninous  materials  may  be  raised  so  as 
to  produce  a  greater  degree  of  fluidity.  It  frequently  happens, 
however,  that  even  under  such  conditions  all  of  the  water  will 
not  separate,  and  the  material  is  then  subjected  to  a  process 
of  dehydration  prior  to  its  further  refining.  When  the  solid 
native  bitumens  contain  impurities  they  invariably  have  to  be 
heated  to  a  rather  high  temperature  before  they  become  suffi- 
ciently fluid  to  separate  from  these  impurities.  In  order  to 
prevent  local  overheating  they  are  usually  agitated  during  the 
process.  Water  and  gas  are  thus  driven  off,  some  of  the  min- 
eral matter  settles  to  the  bottom,  and  the  larger  fragments  of 
vegetable  matter  rise  to  the  surface  and  are  skimmed  off.  The 
mineral  matter  is,  however,  sometimes  so  finely  divided  that 
it  will  not  readily  settle  out,  and  agitation  further  hinders  this 
separation.  Both  finely  divided  mineral  and  vegetable  matter 
therefore  commonly  occur  in  refined  asphalt. 

Dehydration. — Dehydrating  processes  are  designed  primarily 
for  the  removal  of  water  in  bituminous  material  which  will  not 
completely  separate  water  by  sedimentation.  It  is  desirable  to 
do  this  prior  to  distillation  because  of  the  fact  that  the  presence 


12  REFINING    PROCESSES 

of  water  creates  a  tendency  to  foam  when  the  mass  of  bitu- 
minous material  is  heated  to  about  the  temperature  of  boiling 
water.  Dehydrating  plants  vary  considerably  in  design,  but 
those  more  commonly  used  for  petroleums  are  known  as  top- 
ping plants.  In  this  device  the  oil  is  pumped,  frequently  under 
pressure,  through  a  length  of  pipe  containing  a  great  many 
abrupt  bends,  so  that  the  path  of  the  oil  is  exceedingly  devious. 
The  pipe  work  is  set  in  a  furnace  so  that  it  may  be  suitably 
heated,  and  as  the  oil  under  pressure  passes  through  this  pipe 
it  is  heated  to  a  temperature  above  that  of  boiling  water.  This 
pipe  discharges  in  a  spray  into  a  large  expansion  chamber  where 
the  water  and  more  volatile  constituents  separate  in  the  form 
of  vapor,  which  is  condensed  in  a  coil  for  the  recovery  of  light 
condensable  hydrocarbons.  The  hot  oil  passes  through  another 
pipe  direct  to  the  still  or  storage  tank.  One  of  the  most  suc- 
cessful methods  for  dehydrating  viscous  tars  is  to  cause  the 
tars  to  flow  in  thin  films  over  heated  baffle-plates  placed  in  an 
air-tight  chamber  to  which  vacuum  is  applied.  Here  the  water 
and  more  volatile  constituents  pass  off  without  causing  the  tar 
to  foam  dangerously,  and  the  volatile  products  are  then  con- 
densed and  recovered  by  suitable  means 

Fractional  Distillation. — Fractional  distillation  is  that  form  of 
distillation  in  which  the  original  constituents  of  a  mixture  are 
separated  mechanically  and  without  chemical  change.  Petro- 
leums and  tars  are  often  subjected  to  fractional  distillation  in 
the  manufacture  of  bituminous  materials  of  interest  in  highway 
engineering.  The  distillation  is  usually  made  upon  the  crude 
product  which  has  been  partially  separated  from  its  impurities 
by  sedimentation  and  dehydration.  Two  main  classes  of  prod- 
ucts are  obtained  by  distillation:  i.  Distillates  which  pass 
over  into  the  receiver,  and,  2.  Residues  which  remain  in  the 
still.  The  former,  with  a  few  exceptions,  are  of  comparatively 
little  interest  from  the  standpoint  of  highway  engineering.  The 
residues,  however,  often  constitute  the  materials  directly  used 
in  the  treatment  or  construction  of  highways.  As  the  temper- 
ature of  distillation  increases,  more  and  more  of  the  lighter 
products  are  removed  and  the  residues  in  the  still  become  more 


REFINING    PROCESSES  13 

and  more  viscous  until  finally  upon  cooling  they  may  become 
solid.  In  producing  these  residues  for  highway  work,  it  is  of 
prime  importance  that  the  material  suffer  no  chemical  change 
due  to  high  temperatures;  in  other  words,  that  the  hydrocar- 
bons present  should  be  merely  separated  and  not  broken  up 
chemically. 

Cracking. — At  high  temperatures  most  hydrocarbons  tend 
to  break  up  into  other  compounds.  This  is  known  as  cracking, 
and,  as  it  often  injures  the  character  of  the  material  being  dis- 
tilled, precautions  are  ordinarily  taken  to  prevent  cracking. 
The  most  common  means  of  securing  a  separation  of  the  higher 
boiling  constituents  is  to  force  steam  through  the  mass  of  mate- 
rial in  the  still  so  as  to  mechanically  carry  over  certain  com- 
pounds at  temperatures  lower  than  their  normal  boiling  point. 
Certain  tests  are  used  in  connection  with  the  examination  of 
bituminous  materials  to  determine  whether  or  not  they  have 
been  cracked,  and  thereby  injured  by  overheating  during  the 
refining  process. 

Destructive  Distillation. — Destructive  distillation  is  not,  prop- 
erly speaking,  a  refining  process,  but  it  is  of  particular  interest 
in  connection  with  the  incidental  manufacture  of  tars  from  coal 
and  other  materials.  It  consists  of  a  complete  breaking  down 
of  the  original  compounds  present  in  the  material  distilled  by 
the  action  of  very  high  temperatures.  This  results  in  the  for- 
mation of  certain  condensable  products  which  are  known  as 
tars.  In  fact,  the  formation  of  tars  is  dependent  upon  crack- 
ing or  destructive  distillation  of  some  other  material.  When 
these  tars,  however,  are  refined  for  the  purpose  of  producing 
bituminous  road  and  paving  materials,  as  much  care  is  neces- 
sary to  prevent  cracking  during  the  fractional  distillation  as  in 
the  case  of  petroleum  products.  In  other  words,  while  the  tar 
itself  is  produced  by  destructive  distillation,  it  in  turn  must 
not  be  destructively  distilled  or  cracked  when  making  refined 
tar  products. 

Blowing. — Certain  classes  of  bituminous  materials  such  as 
fluid  petroleum  residuums  may  be  transformed  into  semisolid  or 
solid  products  without  material  loss  in  volume  or  weight  by  the 


14  REFINING    PROCESSES 

use  of  air  which  is  injected  into  the  residuum  previously  heated 
to  a  temperature  between  400  and  450°  F.  The  air  at  this  tem- 
perature causes  certain  chemical  reactions  to  take  place  which 
tend  to  unite  two  or  more  fluid  compounds  into  single,  more 
viscous,  or  semisolid  compounds.  This  process  is  known  as  the 
blowing  process,  and  petroleum  residuums  which  are  blown  are 
known  as  blown  petroleums.  The  operation  is  frequently  con- 
ducted in  open  or  semi-open  kettles,  although  the  same  result 
may  be  secured  by  injecting  air  into  the  still  at  a  certain  stage 
of  the  distillation  process  and  then  controlling  the  temperature 
so  that  a  true  distillation  will  not  take  place. 

Fluxing. — The  solid  native  bituminous  materials  are  usually 
too  hard  to  be  used  directly  in  highway  engineering.  After 
preliminary  refining,  which  consists  of  the  partial  or  complete 
removal  of  impurities,  they  are  softened  to  the  desired  con- 
sistency by  combining  or  fluxing  them  with  fluid  or  relatively 
soft  petroleum  residuums.  The  fluxing  process  is  ordinarily 
conducted  in  an  open  tank  or  kettle,  which  may  be  equipped 
with  steam  coils  or  heated  by  direct  fire.  The  hard  bitumen 
is  first  melted  in  thp  kettle,  after  which  the  heated  petroleum 
residuum  or  flux  is  run  in,  in  amount  sufficient  to  produce  a 
finished  product  of  the  desired  consistency.  Rather  prolonged 
agitation  of  the  contents  of  the  kettle  is  required  to  secure  an 
absolutely  uniform  product.  Such  agitation  may  be  obtained 
by  means,  of  a  mechanical  stirring  device,  or  with  steam  or  air. 
Mechanical  agitation  is  preferable  in  certain  respects,  but  it  is 
not  as  efficient  as  the  other  two  methods.  Agitation  with  steam 
is  desirable  from  many  standpoints,  but  invariably  results  in  the 
mechanical  removal  of  some  of  the  lighter  constituents  present. 
Air  agitation,  on  the  other  hand,  causes  some  oxidation  to 
take  place,  although  the  temperatures  employed  are  not  as  high 
as  that  at  which  such  oxidation  becomes  very  pronounced.  In 
both  steam  and  air  agitation,  however,  some  allowance  in  the 
proportions  of  flux  to  be  used  should  be  made  for  unavoidable 
hardening.  This  factor  has  to  be  taken  into  account  at  a 
paving  plant  where  the  fluxing  process  is  employed. 

Cutting-Back. — Distillates  are  sometimes  used  as  fluxes  for 


CLASSIFICATION  OF  BITUMINOUS  ROAD  AND  PAVING  MATERIALS     15 

the  harder  bituminous  materials,  which  are  then  said  to  be 
cut-back.  The  term  "cut-back"  was  originally  applied  to  the 
practice  of  first  distilling  a  bituminous  material  until  the  resid- 
uum was  hard  and  brittle,  in  order  to  obtain  certain  valuable 
products  from  the  heavier  distillates,  after  which  a  portion  of 
the  distillate  was  run  back  or  incorporated  with  the  hard  resid- 
uum to  bring  it  to  the  desired  consistency.  It  has,  however, 
gradually  come  to  be  used  to  denote  the  use  of  a  distillate  as 
a  flux  for  any  natural  or  artificial  residuum. 

Emulsification. — All  bitumens  are  practically  insoluble  in 
water.  If,  however,  a  strong  solution  of  soap  is  used,  the  soap 
acts  as  a  medium  for  holding  the  bitumen  and  water  together 
in  suspension  or  emulsion,  and,  if  properly  made,  such  emul- 
sion may  be  further  mixed  or  diluted  with  water  without  caus- 
ing separation.  Thus  emulsions  of  petroleums,  asphalts,  and 
tars  may  be  obtained  under  suitable  conditions,  and  such 
emulsions  are  used  to  some  extent  in  the  surface  treatment, 
and  even  in  the  construction  of  highways. 

CLASSIFICATION  OF  BITUMINOUS  ROAD  AND 
PAVING  MATERIALS 

Classification  According  to  Use. — Bituminous  materials  as 
directly  used  in  highway  engineering  may  be  conveniently  classi- 
fied according  to  use  as  follows: 

I.     Surface  Treatment: 

a.  Dust  Preventives. 

b.  Carpeting  Mediums. 

c.  Seal-Coating  Materials. 

II.    Incorporation  in  the  Pavement  Structure: 

a.  Bituminous  Cements. 

b.  Bituminous  Fillers. 

c.  Bituminous  Aggregates. 

d.  Impregnating  Materials  for  Wood  Block. 
Materials  used  in  both  surface  treatment  and  the  pavement 

structure  may  be  either  of  native  or  pyrogenous  origin.  This 
is  one  of  the  first  things  to  ascertain  from  a  laboratory  sample. 


16     CLASSIFICATION  OF  BITUMINOUS  ROAD  AND  PAVING  MATERIALS 

The  use  of  further  tests  will  then  in  many  cases  be  determined 
by  the  specific  purpose  for  which  the  material  is  to  be  used 
or  is  supposed  to  be  suitable. 

Dust  Preventives. — Dust  preventives  are  usually  relatively 
thin  fluids  which  may  be  applied  without  preheating.  They 
should  be  susceptible  to  a  light  uniform  distribution  so  as  to 
saturate  the  dust  particles  on  the  road,  but  not  penetrate  the 
road  surface  to  any  extent.  They  need  not  necessarily  possess 
cementitious  properties  nor  develop  cementitiousness  after  ap- 
plication, as  they  are  not  primarily  intended  for  the  construc- 
tion of  bituminous  carpets,  and  if  properly  used  the  treated 
road  rarely  requires  a  covering  of  fine  mineral  matter.  To  be 
of  maximum  service,  they  should  not  volatilize  rapidly  to  any 
extent  under  ordinary  atmospheric  conditions.  Dust  preventives 
in  most  common  use  are: 

1.  Crude  and  Topped  Petroleums. 

2.  Heavy  Petroleum  Distillates. 

3.  Petroleum  Emulsions  and  Emulsifying  OiK 

4.  Crude  and  Dehydrated  Tars. 

Carpeting  Mediums. — Carpeting  mediums  are  usually  viscous 
fluids  and  often  have  to  be  heated  before  they  can  be  satisfac- 
torily applied  to  the  road  surface.  They  should  be  of  such 
normal  consistency  that  when  applied  they  will  not  at  once 
become  so  viscous  as  to  prevent  their  uniform  distribution  and 
adherence  to  a  properly  prepared  surface  of  the  type  of  road 
upon  which  they  are  used.  They  should  possess  or  develop 
shortly  after  application  sufficient  cementitiousness  to  bind 
together  and  hold  in  place  a  covering  of  sand,  fine  gravel,  or 
stone  chips,  with  which  they  combine  to  form  the  m-at  or  carpet. 
They  should  furthermore  waterproof  the  road  surface.  If  they 
contain  a  base  of  high  binding  value  they  may  well  carry  a 
relatively  high  percentage  of  volatile  constituents,  which  after 
application  rapidly  evaporate  and  leave  practically  a  bituminous 
cement  in  place.  The  carpeting  mediums  in  most  common  use  are : 

1.  Residual  Petroleums. 

2.  Cut-back  Asphalt  Cements. 

3.  Residual  or  Refined  Tars. 


CLASSIFICATION  OF  BITUMINOUS  ROAD  AND  PAVING  MATERIALS     17 

Seal-Coating  Materials. — Seal-coating  materials  are  in  reality 
a  superior  type  of  carpeting  medium  applied  to  bituminous- 
constructed  roads.  In  many  cases  they  are  the  same  type  and 
grade  of  bituminous  cement  used  in  the  construction  of  the 
underlying  wearing  course.  While  they  will  adhere  to  a  clean 
bituminous  surface,  they  cannot  be  satisfactorily  used  in  the 
surface  treatment  of  ordinary  gravel  or  macadam  roads. 

Bituminous  Cements. — Bituminous  cements  are  very  viscous 
or  semisolid  materials  whose  function  is  to  bind  and  waterproof 
at  least  the  wearing  course  of  the  road  structure.  Their  requi- 
site binding  strength  and  degree  of  hardness  are  largely  depen- 
dent upon  the  size  and  grading  of  the  mineral  aggregate  which 
they  cement  together  In  general,  the  finer  the  aggregate  the 
greater  becomes  the  necessary  degree  of  solidity  and  binding  power 
of  the  bituminous  cement.  For  the  finer  aggregates,  therefore, 
high  susceptibility  to  temperature  changes  is  to  be  particularly 
avoided.  Thus  refined  tars,  which  are  the  most  susceptible  to 
temperature  changes  of  all  bituminous  materials,  may  be  satis- 
factorily used  in  the  construction  of  bituminous  macadam  or 
coarse  aggregate  bituminous  concrete,  but  are  not  well  suited 
for  use  in  the  fine  aggregate  concretes.  Bituminous  cements 
in  most  common  use  at  present  are: 

1.  Oil  Asphalts. 

2.  Blown  Petroleums. 

3.  Fluxed  Native  Asphalts. 

4.  Very  Viscous  Refined  Tars. 

Bituminous  Fillers. — Bituminous  fillers  may  be  of  the  nature 
of  relatively  hard  bituminous  cements  or  mixtures  of  bituminous 
materials  with  very  finely  divided  mineral  matter.  In  the  former 
case  they  are  most  frequently  heated  to  a  fluid  condition  and 
then  poured  into  the  joints  of  the  pavement.  In  the  latter  case 
they  are  called  prepared  fillers  and  are  often  manufactured  in 
the  form  of  strips  of  proper  width  and  thickness  to  place  in 
the  joints.  The  surface  is  then  sometimes  sealed  with  a  hot  iron. 
Bituminous  fillers  should  adhere  to  the  sides  of  the  joints  and 
waterproof  them.  In  cold  weather  they  should  not  become  so 
hard  as  to  chip  under  traffic,  and  in  hot  weather,  when  the  pave- 


18     CLASSIFICATION  OF  BITUMINOUS  ROAD  AND  PAVING  MATERIALS 

ment  expands,  they  should  not  become  so  fluid  as  to  bleed  and 
produce  a  sticky  surface.  The  principal  types  of  bituminous 
fillers  are: 

1.  Blown  Petroleums  and  Asphalt  Cements. 

2.  Tar  Pitches. 

3.  Mixture  of  Asphalt  Cements  with  Finely  Divided  Silica, 

Limestone  Dust,  or  Clay. 

Bituminous  Aggregates. — Bituminous  aggregates  are  ordinar- 
ily used  to  produce  directly  the  wearing  course  of  a  pavement. 
Many  of  them  are  known  by  names  which  have  come  to  indi- 
cate certain  limitations  of  grading  of  the  mineral  aggregate; 
others  are  known  according  to  their  origin  or  method  of  manu- 
facture. Patents  have  been  granted  upon  various  combinations 
of  mineral  matter  with  bituminous  cements,  and  some  of  these 
combinations  are  used  under  patented  or  trade  names.  The 
important  types  of  bituminous  aggregates  are: 

1.  Binder  Course. 

2.  Sheet  Asphalt  Topping  or  Surface  Mix. 

3.  One  Size  Broken  Stone  Concrete. 

4.  Coarse  Graded  Concrete. 

5.  Fine  Graded  Concrete. 

6.  Bituminous  Gravel  Concrete. 

7.  Bituminous  Earth. 

8.  Rock  Asphalt. 

9.  Asphalt  Block. 

Impregnating  Materials. — Impregnating  materials  are  ordi- 
narily used  in  the  treatment  of  wood  block.  They  should  be 
sufficiently  fluid,  and  free  from  suspended  matter  to  impregnate 
the  block  thoroughly  and  should  possess  sufficient  antiseptic  and 
germicidal  properties  to  prevent  decay  of  the  wood.  They  should 
also  waterproof  it  to  a  very  considerable  extent.  When  used 
in  proper  amount  they  should  not  bleed  from  the  wood  in  warm 
weather  and  produce  a  sticky  surface.  To  be  of  lasting  value, 
they  should  contain  a  relatively  low  percentage  of  highly  vola- 
tile constituents.  Tars  and  tar  products  are  ordinarily  used 
for  this  purpose.  Recently  asphalt  cements  have  been  used  to 
impregnate  building  or  paving  brick,  but  such  products  are  not 


LABORATORY,  SAMPLING,  PREPARATION,  AND  MANIPULATION    19 

usually  termed  impregnating  materials.    The  tar  products  of 
most  importance  are: 

1.  Tar  Distillates. 

2.  Fluid  Refined  Tars. 

3.  Mixtures  of  Refined  Tars  with  Tar  Distillates. 

LABORATORY  SAMPLING,  PREPARATION,  AND 
MANIPULATION 

Representative  Samples. — Samples  of  bituminous  materials  as 
received  by  the  laboratory  are  presumably  representative  of 
the  entire  bulk  of  material  sampled,  whether  it  be  the  con- 
tents of  a  storage  tank,  a  single  batch  of  manufactured  product, 
or  a  consignment  of  material  shipped  in  tank  cars,  barrels,  or 
drums.  Too  often  this  is  not  the  case,  but  methods  of  plant 
and  field  sampling  do  not  come  within  the  scope  of  this  manual, 
and  it  must  therefore  be  assumed  that  the  original  samples 
have  been  properly  taken.  If  evidence  to  the  contrary  exists, 
as  indicated  by  the  presence  of  dirt,  chips  of  wood,  or  other 
apparently  extraneous  materials,  the  laboratory  is  usually  jus- 
tified in  discarding  such  samples,  and  insisting  upon  fresh  ones, 
as  it  is  exceedingly  difficult,  and  often  impossible,  to  remove  the 
extraneous  material  prior  to  making  a  laboratory  examination 
without  in  some  way  changing  the  characteristics  of  the  orig- 
inal material.  Rejection  may  also  properly  be  made  of  samples 
which  have  become  contaminated  or  altered  through  careless 
or  wrong  methods  of  packing  and  shipping.  Thus  it  is  not  at 
all  unusual  to  find  that  a  sample  has  been  in  direct  contact 
with  excelsior,  sawdust,  or  wrapping  paper  which  has  adhered 
to  or  mixed  with  it  during  shipment.  The  presence  of  such  ex- 
traneous matter  may  vitiate  many  of  the  tests  which  it  may 
be  found  necessary  or  desirable  to  make  upon  the  material. 

Size  of  Samples. — While  a  complete  set  of  tests  may  often 
be  made  upon  a  much  smaller  sample,  it  is  usually  desirable 
that  the  laboratory  have  at  hand  not  less  than  a  one-quart 
sample  of  petroleum,  asphalt,  and  tar  products;  not  less  than 
two  pounds  of  rock  asphalt  or  fine  bituminous  aggregate,  and 


20    LABORATORY,  SAMPLING,  PREPARATION,  AND  MANIPULATION 

about  five  pounds  of  coarse  bituminous  aggregate.  In  certain 
cases  two  or  more  samples  may  be  submitted  from  a  single 
shipment  or  lot  of  material  with  the  understanding  that  a  few 
tests  will  be  made  upon  each  to  determine  whether  the  indi- 
vidual samples  are  of  Uniform  character,  and  that  a  complete 
set  of  tests  will  then  be  made  upon  a  composite  sample  pre- 
pared in  the  laboratory  from  equal  proportions  of  the  individual 
samples  submitted.  In  such  cases  the  size  of  the  individual 
samples  should  be  such  as  to  allow  for  the  tests  of  uniformity, 
usually  specific  gravity  and  consistency,  with  a  surplus  amply 
sufficient  to  afterward  prepare  a  single  composite  sample  of 
the  same  size  as  though  only  one  sample  were  submitted.  For 
daily  routine  laboratory  checks  of  plant  or  field  practice,  the 
most  desirable  size  of  sample  will  depend  upon  just  what  check 
tests  are  required.  While  the  laboratory  may  not  always  need 
enough  material  to  make  duplicate  tests,  it  should  always  have 
at  hand  a  sufficient  amount  for  that  purpose,  and  in  addition 
enough  to  file  away  for  possible  future  reference. 

Containers. — For  fluid  products,  a  one-quart  rectangular  can 
with  small,  tight-fitting  screw  top  is  preferable.  For  very  vis- 
cous and  soft  semisolid  products,  a  one-quart  cylindrical  can 
with  tight-fitting  pry  lid,  such  as  commonly  used  for  paints, 
will  be  found  convenient.  For  the  harder  semisolid  and  solid 
products,  a  shallow  rectangular  or  cylindrical  can  with  ordinary 
box  lid  top  is  suitable. 

Identification. — The  laboratory  should  insist  that  all  samples 
submitted  bear  on  the  outside  of  the  container  marks  to  suf- 
ficiently identify  them.  This  would  ordinarily  include  the 
name  and  address  of  the  shipper,  the  tank  or  car  number  from 
which  the  sample  was  taken,  the  location  and  type  of  work  in 
which  it  is  tojbe  used,  and  in  certain  cases  the  name  of  the  manu- 
facturer. If  it  is  to  be  examined  for  conformity  with  any  par- 
ticular specification,  this  fact  should  also  be  indicated.  Upon 
receipt  of  the  sample  this  information  should  be  immediately  re- 
corded in  the  laboratory  note-book  for  the  purpose  of  identifying 
the  sample  with  the  results  of  tests.  An  example  of  such  identi- 
fication is  shown  under  method  of  keeping  laboratory  records. 


LABORATORY,  SAMPLING,  PREPARATION,  AND  MANIPULATION    21 

Laboratory  Sampling. — Even  when  truly  representative  sam- 
ples of  bituminous  materials  are  submitted  to  the  laboratory 
representative  test  results  may  not  be  obtained  by  skilled  oper- 
ators unless  special  precautions  are  taken  to  insure  that  that 
portion  of  the  sample  used  in  a  given  test  is  representative 
of  the  entire  sample.  Thus  segregation  of  certain  constituents 
may  take  place  during  shipment  or  upon  standing,  and  when 
this  is  likely  to  occur  the  first  rule  to  be  observed  is  to  thoroughly 
mix  the  contents  of  the  sample  can  before  removing  a  portion  for 
test.  In  the  case  of  viscous  liquids,  semisolids,  and  solids,  this 
will  usually  necessitate  heating,  in  which  case  extreme  care 
should  be  taken  that  no  loss  by  overheating  takes  place.  The 
material  should  be  mixed  at  the  lowest  practicable  temperature, 
and  preferably  in  the  original  container.  In  the  case  of  bitu- 
minous aggregates  the  mass  of  material  should  be  slowly  warmed 
in  a  shallow  pan  until  the  bituminous  cement  has  sufficiently 
softened  to  allow  its  disintegration  without  fracture  of  the  min- 
eral constituents.  When  composite  samples  are  to  be  prepared, 
equal  quantities  of  the  individual  samples  should  be  weighed 
out  in  a  new  container  and  thoroughly  mixed  at  the  lowest 
practicable  temperature.  Mixing  may  ordinarily  be  accom- 
plished with  a  stirring  rod,  kitchen  knife,  or  kitchen  spoon,  but 
in  the  case  of  crude  products,  when  it  is  desired  to  recombine 
the  bituminous  material  with  water  which  has  separated,  re- 
course may  be  had  to  more  violent  agitation  and  a  small  egg- 
beater  will  often  be  found  useful  for  this  purpose. 

Equipment  for  General  Manipulation. — For  general  laboratory 
manipulation  such  as  heating,  preparing,  and  transferring  bitu- 
minous materials,  the  more  expensive  equipment  of  the  chemical 
laboratory,  such  as  beakers,  flasks,  porcelain  dishes,  spatulas, 
etc.,  may  be  replaced  by  cheaper  kitchen  utensils  and  hardware. 
It  will  be  found  convenient  to  have  at  hand  a  number  of  metal 
saucepans,  stamped  metal  cups  free  from  soldered  joints,  kitchen 
knives,  and  large  heavy  metal  spoons.  The  use  of  agate  or 
enameled  ware  for  heating  bituminous  materials  should  in  gen- 
eral be  avoided  owing  to  its  tendency  to  chip  and  flake  with 
use,  thus  contaminating  the  material  which  is  being  manipulated. 


22          LABORATORY  REPORTS  AND  RECORDS 

An  assortment  of  stamped  tin  boxes  of  various  sizes  and  shapes, 
a  number  of  heavy  glass  stirring  rods,  and  a  pair  of  nickel  cru- 
cible tongs  are  also  useful  for  general  laboratory  handling.  A 
Bunsen  burner  with  tripod  and  asbestos  board  square  and  a 
gas  or  electric  hot  plate  are  ordinarily  sufficient  for  heating 
purposes,  although  a  steam  bath  and  a  hot-air  oven  which 
may  be  maintained  at  a  low  temperature  may  also  often  be 
used  to  advantage  in  preparing  samples  for  analysis. 

LABORATORY  REPORTS  AND  RECORDS 

Laboratory  Notes. — For  recording  observations,  noting  ana- 
lytical data,  and  making  calculations,  the  laboratory  operator 
will  usually  find  some  form  of  note-book  more  convenient  than 
the  card  system.  Loose-leaf  books  holding  letter-size  sheets  are 
in  many  respects  most  convenient,  but  when  any  necessity  may 
exist  for  making  a  chronological  record,  as,  for  instance,  in  con- 
nection with  court  cases,  a  bound  book  is  the  only  style  which 
should  be  used,  and  the  record  should  be  made  and  dated  in 
ink.  Too  frequently  the  laboratory  note-book  constitutes  at 
best  but  a  slovenly  record,  and  in  many  cases  is  decipherable  to 
the  operator  alone,  and  then  only  while  the  work  is  fresh  in  his 
mind.  Little  excuse  exists  for  such  practice,  as  it  does  not  re- 
quire much  more  time  to  keep  a  neat  than  a  careless  note-book. 
Where  a  large  amount  of  routine  work  is  being  conducted, 
rubber  stamps  for  individual  tests,  leaving  blanks  for  numerical 
results,  will  be  found  useful. 

General  Information. — Immediately  upon  receipt  of  a  sample 
by  the  laboratory  it  should  be  given  a  serial  number,  and  a 
dated  record  should  be  made  of  the  identification  which  it  bears. 
Sufficient  space  should  then  be  left  below  this  descriptive  mat- 
ter to  accommodate  all  of  the  analytical  data  which  it  is  ex- 
pected will  be  required.  If  later  it  is  found  that  sufficient 
space  has  not  been  allowed  for  this  purpose,  a  note  should  be 
inserted  that  the  remaining  data  will  be  found  upon  a  subse- 
quent page,  the  number  of  which  is  given.  Before  continuing 
the  notes  on  this  page  the  serial  number  of  the  sample  should 


LABORATORY  REPORTS  AND  RECORDS  23 

be  shown  at  the  top.    A  suggested  form  of  recording  general 
information  is  as  follows: 

No Material Date 

Submitted  by 

Identification  marks 

To  be  examined  for .  . 


Following  the  general  information  it  may  often  be  found 
desirable  to  insert  a  brief  description  of  the  material,  together 
with  a  statement  of  the  condition  in  which  it  is  received. 

Analytical  Data. — Analytical  data  should  be  shown  in  the 
note-book  in  sufficient  detail  to  indicate  the  various  operations 
involved.  All  calculations  should  be  shown  in  the  notes  and 
not  made  upon  a  separate  slip  of  paper  or  scratch  pad.  Errors 
should  not  be  erased  but  should  be  crossed  out.  An  example 
of  a  brief  but  complete  record  of  an  analytical  operation  is  as 
follows: 

TOTAL  BITUMEN 

,Wt.  Flask +12. 5044  Wt.  Crucible    +     20.8416 

Wt.  Flask     10.9032  Wt.  Crucible  20.6863 

Wt.  Sample    1.6012 

Wt.  Insol.  Residue  0.1553 

1.6012)   0.1453     (0.0907=9.07%  org. 

0.144108  Wt.  Ignited  Cruc.  20.6963 

Wt.  Crucible           20.6863 
1192  

1.6012)  o.oiooooo  (0.0062=0.62%  Ash    Wt.  Ash                                   o.oioo 
96072  


39280  Wt.  Organic  Insol.  0.1453 

9.69 
90.31  bit. 


100.00 


Total  bitumen 9O-3i% 

Organic  matter  insoluble 9-°7% 

Ash 0.62% 

Total 100.00% 


24          LABORATORY  REPORTS  AND  RECORDS 

Laboratory  Reports. — The  form  and  substance  of  a  laboratory 
report  should  be  largely  governed  by  circumstances. 

For  strictly  routine  work  of  any  description  a  printed  form 
may  usually  be  devised  which  will  reduce  to  a  minimum  the 
data  which  must  be  added  to  make  the  report  complete.  Where 
the  work  is  not  of  a  routine  nature  the  matter  of  form  may  not 
be  so  readily  handled.  In  either  case,  however,  certain  infor- 
mation should  be  included  which  may  be  covered  by  a  set  form. 
As  an  example  may  be  taken  the  general  form  adopted  by  the 
United  States  Office  of  Public  Roads  and  Rural  Engineering: 

UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 

Office  of  Public  Roads  and  Rural  Engineering 

Washington,  D.  C. 

Sample  No Date 

Report  on 

Identification  Marks 

Known  as 

Submitted  by 


Examined  for , 


Remarks , 


After  "Report  on"  the  type  of  material  should  be  inserted, 
such  as  Oil  Asphalt,  Refined  Tar,  Bituminous  Aggregate,  etc. 
After  "Known  as"  is  given  the  trade  name,  if  the  material 
has  one,  or  any  other  identifying  name.  After  "Examined  for" 
the  purpose  of  the  examination  is  stated,  such  as  identification, 
suitability  for  a  given  purpose,  conformity  with  specifications,  etc. 
Then  should  follow  the  analytical  data  in  tabular  form,  and 
after  "Remarks"  should  be  stated  any  facts  of  peculiar  inter- 
est, particularly  with  reference  to  the  purpose  for  which  the 
material  is  examined.  In  routine  reports  where  it  may  be  desir- 
able to  draw  particular  attention  to  certain  characteristics,  a 


LABORATORY  REPORTS  AND  RECORDS  25 

rubber  stamp  with  arrow  or  pointing  ringer-sign  may  be  used 
with  red  ink  immediately  before  or  after  the  analytical  result 
to  which  attention  is  called.  An  explanation  of  the  meaning  of 
this  sign  should  then  be  given  under  remarks.  Thus  when  a 
material  is  examined  for  conformity  with  a  given  specification, 
the  stamp  may  be  used  to  call  attention  to  all  analytical  results 
which  do  not  fall  within  the  specification  limits.  Typical  exam- 
ples of  routine  reports  are  as  follows.  In  certain  cases  it  may  be 
found  more  desirable  to  submit  a  report  on  a  card  form  than  on 
paper.  If  paper  be  used  it  is  preferable  to  have  the  form  of 
ordinary  letter  size  for  convenient  riling  by  the  recipient.  Unusual 
sizes  should  be  avoided. 

JONES  AND  BROWN 
CHEMICAL   ENGINEERS 

563  Broadway 

Sample  No.  9436  New  York,  July  I,  1916 

Report 

on 
Shipment  of  Asphalt  Cement 

Submitted  by  Wm.  A.  Smith,  City  Engineer,  Greenville,  N.  J. 

Identification.     Three  samples  marked  A,  B,  and  C  respectively.     "Cemento 
Asphalt"  C.  R.  R.  of  N.  J.  36074. 

Examined  for  conformity  with  Greenville  specifications,  Sheet  Asphalt  Pave- 
ment, Mar.  i,  1916. 

Saniple  ABC 

Specific  Gravity  2^/25°  C.  1 . 045  1 . 043 

Penetration  25°  C.,  100  g.,  5  sec.  58  56  57 

Composite  Sample 

Specific  Gravity  25°/25°  C.,  average  (2) 1 .044 

Flash  Point  (open  cup) 245°  C-f- 

Melting  Point  (ring  and  ball) 50°  C. 

Penetration  25°  C.,  100  g.,  5  sec.,  average  (3) 57 

Penetration  O°  C.,  200  g.,  i  min 18 

Loss  163°  C.,  5  hrs.,  50  g 0.7% 

Penetration  residue  25°  C.,  100  g.,  5  sec 34 

Total  bitumen  (soluble  in  CS2) 99 . 90% 

Organic  matter  insoluble 0.05% 

Inorganic  matter  insoluble o. 05% 

100.00% 

Bitumen  insoluble  in  86°  B.  naphtha 28.5% 

Bitumen  insoluble  in  carbon  tetrachloride 0.0% 

Fixed  carbon 18 . 5% 

Remarks: — This  material  conforms  with  specifications. 

Respectfully  submitted, 

JONES  AND  BROWN. 


26 


LABORATORY  REPORTS  AND  RECORDS 


JONES  AND   BROWN 
CHEMICAL  ENGINEERS 

563  Broadway 
Sample  No.  9872  New  York,  Aug.  3,  1916 

Daily  Report 

on 
Sheet  Asphalt  Topping 

Submitted  by  Wm.  A.  Smith,  City  Engineer,  Greenville,  N.  J. 

Identification.     Sample   16,  laid  Aug.   2-16,   Poplar  St.  at  intersection  of 
Third  Street.     From  load  received  at  1 1 :  oo  A.M. 

Examined  for  conformity  with  Greenville  Specifications  Sheet  Asphalt  Pave- 
ment, Mar.  i,  1916. 


Original 
Total  bitumen  (soluble  in  CS2) 10.8 


Pas 

sing  200  me 
100  me 
80 
50 
40 
30 

20 
10 

sh  ....--  -   A  2-4— 

sh,  reta 

ned  o 

n  200  me 

100 

80 
50 
40 
30 

20 

;sh 

..  15-5 

..   7.7 
...  25.8 
..  14.6 

.  .   II.  O 

..   6.1 
4-3 

18.2 

30.3 
17.2 
13.0 

7.2 

5-0 


Sand  Basis 

27-3 
47-5 
25.2 


Total 100.00% 


100.0%     100.0% 


Remarks: — This  sample  shows  a  decided  deficiency  in  filler. 
Note: — f  Indicates  variation  from  specification. 

Respectfully  submitted, 

JONES  AND  BROWN. 

Laboratory  File  Records. — It  is  highly  desirable  that  the  lab- 
oratory retain  a  carbon  copy  of  all  reports  which  it  makes. 
Under  ordinary  conditions  these  copies  may  be  conveniently 
kept  in  a  vertical  letter  file  in  tabbed  folders  bearing  the  name 
of  the  locality  from  which  the  material  is  submitted,  or  the 
name  of  the  party  submitting  the  sample.  In  addition  it  is 
highly  advantageous  to  keep  a  card-abstract  file  according  to 
the  laboratory  serial  number  and  to  cross-reference  this  file 
according  to  type  of  material  and  the  name  of  the  manufac- 
turer or  the  party  who  submits  samples.  The  most  convenient 
and  efficient  system  for  any  particular  laboratory  will  of  course 


LABORATORY  REPORTS  AND  RECORDS  27 

depend  upon  the  general  character  of  the  work  that  the  labora- 
tory is  required  to  do. 

In  the  case  of  the  card-abstract  serial-number  file,  a  5"  by 
8"  card  is  suggested,  bearing  the  following  information  in  addi- 
tion to  the  abbreviated  analytical  results. 


Serial  Number, 

Material 

Submitted  by 

Identification 

Examined  for 

Date  received Date  reported Analyst . . 


PART  H— METHODS  OF  TESTING 
DENSITY  TESTS 

SPECIFIC  GRAVITY 

jBasis  of  Determination 

The  specific  gravity  of  most  bituminous  materials  used  in 
highway  engineering  is  based  upon  the  relative  weights  of  equal 
volumes  of  the  bituminous  material  and  water  at  normal  tem- 
perature, and  is  usually  expressed  as  "  Specific  Gravity  2$°/2$°  C." 
As  the  weight  of  a  given  volume  of  any  material  varies  at  differ- 
ent temperatures,  the  temperature  basis  of  comparison  should 
always  be  indicated  for  very  accurate  work.  A  few  bituminous 
materials,  such  as  certain  tar  distillates,  separate  solid  matter, 
mostly  napthalene,  at  25°  C.,  and  as  this  makes  it  difficult  to 
determine  the  specific  gravity  at  that  temperature,  the  determi- 
nation is  sometimes  made  at  a  temperature  sufficiently  high 
to  insure  complete  fluidity.  When  this  is  done,  water  at  the 
same  temperature  or  at  25°  C.  may  be  taken  as  unity.  In  either 
case  the  basis  of  comparison  should  be  indicated.  Thus  if  the 
weight  of  a  given  volume  of  the  material  is  obtained  at  X°  C. 
and  compared  with  water  at  25°  C.,  the  basis  of  comparison 
should  be  expressed  as  Mows:  "Sp.  Gr.  X°/25°  C."  An  older 
temperature  basis  of  comparison,  which  is  still  used  to  a  consid- 
erable extent  by  manufacturers  and  also  by  the  United  States 
Government,  in  the  calibration  of  the  volume  of  tank  cars  and 
other  containers,  is  15.5°  C.  (60°  F.).  If  the  coefficient  of  expan- 
sion of  the  material  is  known  and  the  specific  gravity  basis  of 
comparison  is  given,  it  is  very  easy  to  translate  any  given  deter- 
mination to  terms  of  another  basis  of  comparison.  Such  a 
method  is  commonly  employed  by  manufacturers  who  for  the 

29 


30  HYDROMETER   METHOD 

sake  of  simplicity  and  rapidity  prefer  to  make  use  of  a  hydrom- 
eter in  the  case  of  many  materials  which  have  to  be  first 
rendered  more  fluid  by  the  application  of  heat.  In  reporting 
the  specific  gravity  of  fluid  bituminous  materials  it  is  not  un- 
common to  express  results  to  four  places  to  the  right  of  the 
decimal  point.  Three  decimal  places  is  usually  reported  in  the 
case  of  semisolid  and  solid  materials,  owing  to  the  fact  that  the 
limit  of  accuracy  is  exceeded  beyond  this  point. 

Hydrometer  Method 

Equipment: 

i  hydrometer  jar  approximately  35  centimeters  long  and  5 
centimeters  in  diameter.  (Fig.  la.) 

i  i-pint  tin  cup,  seamless  type.     (Fig.  ib.) 

i  enamelware  dish  approximately  2  inches  deep  and  9  inches 
in  diameter.  (Fig.  ic.) 

i  chemical  thermometer  reading  from— 10°  C.  to  no°C. 
(Fig.  id.) 

i  set  of  hydrometers — those  with  a  double  scale  at  15.5°  C. 
(60°  F.) — one  for  Baume  and  one  for  a  direct  specific  gravity 
reading  to  the  third  decimal  place — are  convenient.  (Fig.  le.) 

i  hydrometer  reading  from  0.800  to  0.900  specific  gravity. 

i  hydrometer  reading  from  0.900  to  i.ooo  specific  gravity. 

i  hydrometer  reading  from  i.ooo  to  1.200  specific  gravity. 

i  hydrometer  reading  from  1.200  to  1.400  specific  gravity. 
Method. — The  specific  gravity  of  thin  fluid  bituminous  road 
materials  is  most  readily  determined  by  means  of  a  hydrometer 
when  a  sufficient  quantity  is  available  for  the  purpose.  The 
Baume  scale  for  liquids  lighter  than  water  is  commonly  used  by 
petroleum  refiners,  and  many  oil  products  are  sold  upon  a  Baume 
degree  basis.  The  Baume  scale  for  bituminous  materials  heavier 
than  water  is,  however,  seldom  used. 

This  test  is  made  with  the  above-mentioned  apparatus  by 
first  pouring  a  sufficient  quantity  of  the  material  into  the  tin 
cup,  which  is  then  placed  in  the  large  dish  containing  cold 


HYDROMETER    METHOD 


31 


or  warm  water  as  occasion  may  require.  The  material  in  the 
cup  should  be  stirred  with  the  thermometer  until  it  is  brought 
to  a  temperature  of  25°  C.,  after  which  it  should  be  immediately 
poured  into  the  hydrometer  jar  and  its  gravity  determined  by 
means  of  the  proper  hydrometer.  In  case  the  hydrometer  sinks 
slowly,  owing  to  the  viscosity  of  the  material,  it  should  be 
given  sufficient  time  to  come  to  a  definite  resting  point,  and 
this  point  should  be  checked  by  raising  the  hydrometer  and 
allowing  it  to  sink  a  second  time.  The  hydrometer  should 
never  be  pushed  below  the  point  at  which  it  naturally  comes 


FIG.  I.     Hydrometer  Method  of  Determining  Specific  Gravity 

to  rest  until  the  last  reading  has  been  made.  It  may  then 
be  pushed  below  the  reading  for  a  distance  of  three  or  four 
of  the  small  divisions  on  the  scale,  whereupon  it  should  imme- 
diately begin  to  rise.  If  it  fails  to  do  so,  the  material  is  too 
viscous  for  the  hydrometer  method,  and  the  pycnometer  method 
should  be  employed. 

Most  hydrometers  are  based  upon  specific  gravity  at 
i5.5°/i5'5°  C.  If  the  material  tested  is  at  25°  C.,  it  is  evident 
that  without  taking  into  account  the  coefficient  of  expansion 
of  the  hydrometer  itself,  the  actual  basis  of  comparison  is  then 


WESTPHAL    BALANCE    METHOD 


25°/I5-5°  C.  For  all  practical  purposes  this  may  be  converted 
to  the  25°/25°  C.  basis  by  multiplying  the  reading  obtained  by 
the  factor  1.002,  which  corrects  for  the  decrease  in  weight  of  a 
unit  volume  of  water  raised  from  15.5°  to  25°  C.  If  the  specific 
gravity  is  obtained  at  a  considerably  elevated  temperature,  the 
coefficient  of  expansion  of  the  hydrometer  itself  should  be  taken 
into  account  as  well  as  that  of  the  water  and  the  material 
examined. 

When  double-scale  hydrometers  are  not  available,  the  results 
obtained  by  one  scale  may  be  transposed  to  the  other  by  means 
of  the  following  formulas  for  liquids  lighter  than  water: 

T4°  _  0~ 


B.  = 


140 


From  these  formulas  it  will  be  seen  that  i.ooo  specific  gravity  is 

the  equivalent  of  10°  B.,  and 
that  as  specific  gravities  de- 
'Tl1  jl1  |i'  Ji'2  crease    the    degrees    Baume 


increase. 


Westphal  Balance  Method 

A  Westphal  balance  (see  Fig.  2) 
is  convenient  for  quickly  deter- 
mining the  specific  gravity  of  com- 
paratively small  quantities  of  fluid 
bituminous  materials,  particularly 
fluid  distillates.  By  using  a 
vertical  cylindrical  container  of 
about  5/8-inch  diameter,  it  may 
be  possible  to  use  this  instrument 
with  as  little  as  15  c.c.  of  ma- 
terial. 

The  determination  is  made  by 
balancing  a  plummet  in  the  liquid, 
the  scale  of  the  balance  and  the 
weights  used  being  so  designed  as 
to  give  direct  specific  gravity  read- 
ings. The  Westphal  balance  is 
usually  calibrated  for  15. 5% 5 -5° 
C.  determinations,  and  the  results 

obtained  are  subject  to  the  same   corrections   as   noted  under  the  hydrom- 
eter method. 


FIG.  2.     Westphal  Balance 


SPRENGEL    OR    NICOL    TUBE    METHOD  33 

Sprengel  or  Nicol  Tube  Method 
Equipment: 

i  Sprengel  or  Nicol  tube  with  fine  wire  support. 

i  2o-cubic  centimeter  low-form  glass  beaker. 

i  4oo-cubic  centimeter  low-form  glass  beaker. 

i  chemical  thermometer  reading  from  — 10°  C.  to  110°  C. 

i  Bunsen  burner  and  rubber  tubing. 

i  iron  tripod  with  wire  gauge. 

i  glass  stirring  rod. 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 
milligrams. 

i  piece  of  blotting  paper. 

Method. — This  method  is  well  adapted  for  determining 
the  specific  gravity  of  very  small  quantities  of  thin  fluid 
bitumens  or  such  materials  as  tar  distillates  containing  pre- 
cipitated solids  at  normal  temperature.  In  the  latter  case 
the  determination  should  be  made  at  an  elevated  temper- 
ature such  as  38°  C.  (100°  F.)  in  order  to  have  the  material 
completely  fluid. 

The  Nicol  tube,  as  shown  in  Fig.  3,  may  be  made  with 
a  capacity  as  low  as  0.5  c.c.  It  may  be  conveniently  suspended 
by  means  of  a  fine  wire  from  the  hook  on 
one'  of  the  pan  supports  of  the  analytical 
balance.  One  arm  of  the  tube  is  drawn  out 
to  a  fine  capillary  opening.  The  other  arm  is 
somewhat  larger  but  open,  and  carries  a 
mark  to  which  the  instrument  is  filled  by  pIG  3  Nicol  -j^^ 
sucking  in  the«  material  through  the  smaller 
arm.  Any  excess  beyond  the  mark  may  be  removed  by  means 
of  a  small  piece  of  blotting  paper. 

The  test  is  made  by  first  weighing  the  clean  dry  tube  and 
then  weighing  it  filled  with  water  at  normal  or  other  tempera- 
ture, according  to  the  desired  basis  of  comparison.  The  tube 
is  next  emptied  and  thoroughly  dried  by  means  of  a  current 
of  air.  It  is  then  filled  with  the  material  under  examination 
and  again  weighed.  Small  quantities  of  the  material  may  be 
conveniently  handled  in  the  2o-c.c.  beaker,  and  the  larger  beaker 


34  PYCNOMETER    METHOD 

filled  with  water  at  the  desired  temperature  may  be  used  as  a 
control  bath  when  filling  the  instrument. 

Calling  the  weight  of  the  empty  tube  a,  its  weight  filled 
with  water  b,  and  its  weight  filled  with  the  material  under 
examination  c,  the  specific  gravity  may  be  calculated  from  the 
following  formula: 

Specific  Gravity  =  7 . 

0    d 

fr 

Pycnometer  Method 
Equipment: 

i  large  metal  kitchen  spoon. 

i  steel  spatula  or  kitchen  knife. 

i  Bunsen  burner  with  rubber  tubing. 

i  25o-cubic  centimeter  low-form  glass  beaker. 

i  chemical  thermometer  reading  from  — 10°  C.  to  110°  C. 

i  special  pycnometer.     (Fig.  4.) 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 

milligram. 

Method. — The  inconvenience  and  difficulty  of  employing  the 
ordinary  narrow-neck  pycnometer  when  determining  the  specific 
gravity  of  viscous  fluid  and  semisolid  bitumens  have  led  to  the 
use  of  the  special  form  shown  in  Fig.  4. 

This  pycnometer  consists  of  a  fairly  heavy, 
straight-walled  glass  tube,  70  millimeters  long 
and  22  millimeters  in  diameter,  carefully 
ground  to  receive  an  accurately  fitting  solid 
glass  stopper  with  a  hole  of  1.6  millimeters 
bore  in  place  of  the  usual  capillary  opening. 
The  lower  part  of  this  stopper  is  made 
concave  in  order  to  allow  all  air-bubbles  to 
F*  H  bb  d  escaPe  through  the  bore.  The  depth  of  the 

Pycnometer        cup-shaped  depression  is  4.8    millimeters    at 
the  center.    The  stoppered  tube  has  a  capacity 
of  about  24  cubic  centimeters,  and  when  empty  weighs  about  28 
grams.     Its  principal  advantages  are  (i)  that  any  desired  amount 
of  bitumen  may  be  poured  in  without  touching  the  sides  above 


PYCNOMETER   METHOD  35 

the  level  desired;  (2)  it  is  easily  cleaned;  (3)  on  account  of  the 
i. 6-millimeter  bore,  the  stopper  can  be  more  easily  inserted 
when  the  tube  is  filled  with  a  very  viscous  oil  than  if  it  contained 
a  capillary  opening. 

When  working  with  semisolid  bitumens  which  are  too  soft 
to  be  broken  and  handled  in  fragments,  the  following  method 
of  determining  their  specific  gravity  is  employed.  The  clean 
dry  pycnometer  is  first  weighed  empty,  and  this  weight  is  called 

a.  It  is  then  filled  in  the    usual   manner   with   freshly   dis- 
tilled water  at  25°  C.,  and  the  weight  is  again  taken  and  called 

b.  A  small  amount  of  the  bitumen  should  be  placed  in  the 
spoon  and  brought  to  a  fluid  condition  by  the  gentle  applica- 
tion of  heat,  with  care  that  no  loss  by  evaporation  occurs.    When 
sufficiently  fluid,  enough  is  poured  into  the  dry  pycnometer, 
which  may  also  be  warmed,  to  fill  it  about  half  full,  without 
allowing  the  material  to  touch  the  sides  of   the   tube   above 
the  desired  level.     The  tube  and  contents  are  then  allowed  to 
cool  to  room  temperature,  after  which  the  tube '  is  carefully 
weighed  with  the  stopper.     This  weight  is  called  c.    Distilled 
water,  at  25°  C.,  is  then  poured  in  until  the  pycnometer  is  full. 
After  this  the  stopper  is  inserted,  and  the  whole  cooled  to  25°  C. 
by  a  3o-minute  immersion  in  a  beaker  of  distilled  water  main- 
tained at  this  temperature.    All  surplus  moisture  is  then  re- 
moved with  a  soft  cloth,  and  the  pycnometer  and  contents 
are  weighed.    This    weight    is    called   d.    From  the    weights 
obtained  the  specific  gravity  of  the  bitumen  may  be  readily 
calculated  by  the  following  formula: 

Specific  Gravity  25°  C./25°  C.  =  (ft  _  ^  "  ^  _  ^ 

Both  a  and  b  are  constants  and  need  be  determined 
but  once.  It  is,  therefore,  necessary  to  make  but  two  weighings 
for  each  determination  after  the  first.  Results  obtained  accord- 
ing to  the  method  given  above  are  accurate  to  within  2  units 
in  the  third  decimal  place,  while  the  open- tube  method  is  accu- 
rate to  the  second  decimal  place  only 

The  specific  gravity  of  fluid  bitumens  may  be  determined  in 
the  ordinary  manner  with  this  pycnometer  by  completely  filling 


36 


DISPLACEMENT    METHOD 


it  with  the  material  and  dividing  the  weight  of  the  bitumen  thus 
obtained  by  that  of  the  same  volume  of  water. 

The  pycnometer  may  be  readily  cleaned  by  placing  it  in  a 
hot-air  bath  until  the  bitumen  is  sufficiently  fluid  to  pour.  As 
much  is  drained  out  as  possible  and  the  interior  swabbed  with 
a  piece  of  cotton  waste.  It  is  then  rinsed  clean  with  a  little 
carbon  disulphide,  and  after  drying  is  again  ready  for  use. 


Displacement  Method 
Equipment: 

i  chemical  thermometer  reading  from  —  10°  C.  to  110°  C. 
i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 

milligram. 

i  wood  or  metal  platform. 
i  i5o-cubic  centimeter  low-form  glass  beaker. 
i  piece  of  fine  silk  thread. 

Method.  —  For  materials  which  are  hard  enough  to  be  broken 
and  handled  in  fragments  at  room  temperature,  the  following 
method  will  prove  convenient.  A  small  fragment  of  the  bitu- 
men (about  i  c.c.)  is  suspended  by  means  of  a  silk  thread  from 
the  hook  on  one  of  the  pan  supports,  about  1^2  inches  above 
the  pan,  and  weighed.  This  weight  is  called  a.  It  is  then 

weighed  immersed  in  water  at 
25°  C.,  as  shown  in  Fig.  5,  and 
this  weight  is  called  b.  The 
specific  gravity  may  then  be 
calculated  by  means  of  the 
following  formula: 


a 


Specific  Gravity  =     _  ,  • 


FIG.  5.     Displacement  Method  of 
Determining  Specific  Gravity 


This  method  may  be  used  in 
the  determination  of  the  specific 
gravity  of  compressed  bitumi- 
nous aggregates  such  as  sections  of  bituminous  pavement, 
asphalt  block,  etc.  In  the  case  of  coarse  aggregates,  when 
it  is  desirable  to  run  the  test  upon  a  large  sample,  a  rough 


METHOD    FOR    COARSE    MINERAL    AGGREGATES 


37 


balance,  sufficiently  sensitive  to  accurately  give  specific  gravity 
determinations  to  within  2  units  in  the  third  significant 
figure,  may  be  rigged  up  on  the  edge  of  a  table,  so  that 
the  sample  may  be  suspended  in  a  bucket  of  water  from 
one  of  the  pan  supports.  As  bituminous  aggregates  may  fre- 
quently absorb  water  during  the  test,  it  is  advisable  to  deter- 
mine their  apparent  specific  gravity.  This  may  be  done  by 
first  weighing  the  specimen  in  air  and  then  immersing  it  in 
water  for  24  hours.  The  specimen  is  then  removed  from  the 
water,  rapidly  surface-dried  with  a  piece 
of  cloth,  and  again  weighed  in  air.  It  is 
then  weighed  immersed  in  water.  Call- 
ing the  original  weight  in  air  a,  the 
weight  in  air  after  absorption  b,  and  the 
weight  in  water  c,  the  apparent  specific 
gravity  is  calculated  by  means  of  the 
following  formula: 

Apparent  Specific  Gravity  =  7 . 

Method  for  Coarse  Mineral  Aggregates 

A  convenient  apparatus  for  determining  the 
specific  gravity  of  coarse  mineral  aggregates  is 
shown  in  Fig.  6.  It  consists  of  a  brass  cup,  "A," 
4.K  inches  in  diameter  and  6^4  inches  high,  which 
is  fitted  with  a  conical  cap,  "B."  The  sides  of 
the  cup  are  turned  down  at  the  top  one-half  the 
thickness  of  the  metal,  forming  a  shoulder  about 
one  inch  deep.  A  similar  shoulder  cut  in  the  cap 
provides  an  absolutely  constant  volume  when  the 
cap  is  in  position.  The  joint  is  made  water-tight 
by  snapping  an  ordinary  rubber  band  about 
K  inch  wide  around  it.  A  glass  tube,  "  C, "  with 
a  single  graduation  fixes  the  volume  of  the  cup. 
A  special  form  of  burette,  "  D,"  carrying  two  bulbs 
of  200  and  600  c.c.  capacity,  and  a  graduated  tube 
of  200  c.c.  capacity,  capable  of  being  read  to  the 
nearest  cubic  centimeter,  is  conveniently  used 


~  .,.,..  •,,,,,,7. 


FIG.  6. 


H  ubbard- Jackson 

nearest    cuuic    centimeter,   is  conveniently    uscu    c  r*        •*      A 

for  measuring  the  water,  although  the  water  may    Specific-Gravity  Apparatus 
be  weighed  from  a  looo-c.c.  glass  flask  if  desired. 

When  making  a  determination,  a  sample  of  the  material  weighing  about 
1000  grams  is  first  dried  to  constant  weight  in  an  oven  at  110°  C.,  cooled,  and 
accurately  weighed  to  the  nearest  0.5  gram.  It  is  then  immersed  in  water  for 
24  hours,  after  which  it  is  surface-dried  with  a  towel,  reweighed,  and  immediately 
introduced  into  the  brass  cup.  The  cap  is  then  placed  in  position  and  the 
cup  filled  with  water  from  the  burette  up  to  the  graduation,  "C."  Knowing 


38 


METHOD    FOR    FINE    MINERAL    AGGREGATES 


the  volume  of  the  cup,  the  apparent  specific  gravity  of  the  material  may  be 
calculated  as  follows:  Calling  the  weight  of  the  dry  sample  in  air  a,  the  total 
volume  of  the  cup  b,  and  the  volume  of  water  necessary  to  fill  it  after  introduc- 
ing the  sample  c,  then 

Apparent  Specific  Gravity  =  7 — • 

o — c 

When  it  is  desired  to  obtain  as  nearly  as  possible  the  apparent  specific 
gravity  of  aggregates  consisting  of  a  mixture  of  coarse  and  fine  particles,  it  is 
advisable  to  separate  a  weighed  sample  of  the  material  by  means  of  a  ,K-inch. 
screen  and  to  make  an  apparent  specific  gravity  determination  upon  about 
1000  grams  of  the  coarse  fraction  and  a  true  specific  gravity  determination 
upon  not  less  than  50  grams  of  the  finer  fraction  by  the  method  for  fine  mineral 
aggregates.  The  specific  gravity  of  the  whole  may  then  be  calculated  from 
the  following  formula,  where  W  equals  the  weight  per  cent  of  coarse  aggregate, 
Wl  the  weight  per  cent  of  fine  aggregate,  and  G  and  G1  their  respective  specific 
gravities: 

Approximate  Apparent  Specific  Gravity  =  w/C  4-  Wl/Gl" 

This  method  is  used  because  it  is  impracticable  to  surface-dry  a  large  mass 
of  particles  smaller  than  %  inch  in  diameter. 

Method  for  Fine   Mineral  Aggregates 

The  apparatus  used  in  this  method  is  shown  in 
Fig.  7,  and  consists  of  an  Erlenmeyer  flask,  fitted 
with  a  special  form  of  hollow  ground-glass  stopper, 
and  having  a  capacity  of  200  c.c.  up  to  the  gradua- 
tion on  the  stopper  tube.  A  special  form  of  burette 
with  graduations  to  o.oi  in  specific  gravity,  pro- 
vided with  a  bulb  of  180  c.c.  capacity,  is  conveni- 
ently used  for  measuring  the  water  displaced.  In 
making  the  specific  gravity  determination,  the 
burette  is  first  filled  with  water  to  the  mark  above 
the  bulb.  Water  is  then  run  into  the  flask  until 
the  burette  bulb  is  about  half  empty.  A  sample 
of  sand  or  other  fine  aggregate  dried  to  constant 
weight,  and  weighing  to  within  o.oi  gram  of  50 
grams,  is  then  slowly  introduced  into  the  flask, 
after  which  the  hollow  ground-glass  stopper  is  in- 
serted and  the  flask  filled  with  water_  up  to  the 
graduation  on  the  stopper.  The  specific  gravity 
may  then  be  read  directly  on  the  burette.  It  is 
important  that  throughout  this  test  the  water  be 
kept  at  a  constant  temperature,  and  that  all  en- 
tangled air-bubbles  in  the  aggregate  and  on  the 
sides  of  the  flask  be  removed  by  agitation. 

Value  of  Specific-Gravity  Determination 

A  specific-gravity  determination  is 
commonly  made  upon  all  types  and  grades 
of  bituminous  materials,  with  the  excep- 
tion of  loose  or  uncompressed  bituminous  aggregates.  It  is  one  of 
the  most  valuable  means  of  identifying  a  bituminous  material, 


FIG.  7.   Jackson  Specific- 
Gravity  Apparatus 


VALUE    OF    SPECIFIC-GRAVITY    DETERMINATION 


39 


particularly  in  connection  with  a  test  of  consistency.  When 
considered  in  connection  with  other  tests  it  is  also  often  of 
service  in  determining  the  suitability  of  a  material  for  a  given 
use.  In  specifications  it  is  used  for  both  purposes  and  also 
for  the  sake  of  controlling  uniformity  of  supply  from  a  given 


Heavy  Residual  Coal  Tars 
Light  Residual  Coal  Tars 
Heavy  Residual  Water  Gas  Tars 

Light  Residual  Water  Gas  Tars 
Creosoting  Oils 


1.4 


1.- 


l.u 


Cu 


ban  Asphalt 


GrahamTBa 


•MaracaiboAsplialt 


Bermudez  Asphalt 
Gilsonite 

Malthas 

Oil  Asphalts  and  very 
heavy  Residues 

I  Heavy  Residues  and 
Fluxes 

Light  Residues  and 
Fluxes 


FIG.  8.     Specific-Gravity  Chart  for  Bituminous  Materials 

source.  For  this  reason  it  is  particularly  valuable  in  the  exam- 
ination of  a  number  of  samples  from  a  given  shipment  or  lot 
of  material  before  making  a  complete  analysis  of  a  composite 
sample.  Thus,  individual  samples  from  a  given  lot  of  material 
will  almost  invariably  be  of  uniform  character  if  they  have  the 
same  specific  gravity  and  consistency  test  values. 

In  general,  bituminous  materials  tend  to  classify  themselves 


40  COEFFICIENT    OF    EXPANSION 

according  to  specific  gravity  as  illustrated  by  Fig.  8.  The  pure 
bitumen  of  petroleum  and  asphalt  products  seldom  exceeds 
1.055  and  of  tars  1.18.  A  higher  specific  gravity,  therefore, 
usually  indicates  the  presence  of  mineral  matter  or  heavy 
inorganic  impurities,  such  as  free  carbon. 

In  the  distillation  of  crude  bituminous  materials  the  specific 
gravity  of  the  residue  in  the  still  increases  as  distillation  pro- 
gresses. The  first  distillates  obtained  have  a  relatively  low  spe- 
cific gravity,  and  as  the  temperature  of  distillation  increases  the 
specific  gravity  of  the  distillate  also  increases.  The  specific 
gravity  of  bituminous  materials  is  so  nearly  additive  that  in 
both  fractional  distillation  and  fluxing  a  close  approximation  of 
the  specific  gravity  of  the  whole  or  any  particular  portion  may 
be  made  if  the  gravity  and  proportion  of  the  other  factors  are 
known.  Thus,  if  the  specific  gravities  of  an  asphalt  cement  and 
the  refined  asphalt  from  which  it  is  produced  are  known,  together 
with  the  proportions  of  R.  A.  and  flux  used  in  the  manufacture 
of  the  A.  C.,  the  specific  gravity  of  the  flux  may  be  calculated 
with  a  fair  degree  of  accuracy. 

As  bituminous  materials  are  commonly  purchased  and  used 
upon  both  a  weight  and  volume  basis,  the  specific-gravity  deter- 
mination is  of  frequent  use  in  translating  volume  units  to  weight 
units,  and  vice  versa.  In  the  laboratory  this  use  of  the  deter- 
mination is  of  particular  interest  in  comparing  the  bitumen 
contents  of  various  bituminous  aggregates.  Moreover,  in  the 
examination  of  compressed  bituminous  aggregates  it  is  of  very 
material  use  in  determining  the  degree  of  compression  or  percen- 
tage of  voids  which  are  present.  It  is  also  used  in  determining 
the  coefficient  of  expansion  of  bituminous  materials. 

COEFFICIENT   OF  EXPANSION 

Basis  of  Determination 

The  coefficient  of  volume  or  cubical  expansion  of  any  sub- 
stance is  the  ratio  between  the  increase  in  volume  which  it 
undergoes  when  its  temperature  is  raised  one  degree  and  its 
original  volume.  The  original  or  unit  volume  is  set  at  some 


SPECIFIC-GRAVITY   METHOD  41 

standard  temperature.  In  the  case  of  bituminous  materials, 
normal  temperature,  25°  C,  is  convenient  to  use,  although,  for 
the  same  reason  that  the  specific-gravity  determination  may 
be  required  at  15.5°  C.,  this  temperature  is  also  sometimes  taken 
as  standard.  The  coefficient  of  expansion  may  be  expressed 
either  in  terms  of  the  Centigrade  or  Fahrenheit  scale.  If  K 

T7-O  "C1 

represents  the  coefficient  of  expansion,  then  K  °  C.  =  —   —  *  and 

c  K°  C* 
K°F.=  -  -  '-.    The  coefficient  of  expansion  of  most  materials 

varies  slightly  at  different  temperatures,  and  for  this  reason  the 
volume  change  which  is  undergone  between  comparatively  wide 
ranges  of  temperature  is  divided  by  the  number  of  degrees  of 
temperature  and  the  average  coefficient  of  expansion  calculated. 
It  is  the  average  coefficient  of  expansion  of  bituminous  mate- 
rials which  is  of  most  interest  from  a  practical  standpoint.  As  a 
material  expands  under  the  action  of  heat,  its  specific  gravity 
becomes  less.  It  is  thus  possible  to  calculate  K  from  volume 
measurements  at  different  temperatures  or  from  specific-gravity 
determinations  at  different  temperatures. 

Specific-Gravity  Method 

In  this  determination  it  is  usually  most  convenient  to  use 
the  pycnometer  method  of  determining  the  specific  gravity  of 
the  material  at  normal  temperature.  The  weight  of  the 
water  content  of  the  pycnometer  at  any  desired  elevated  tem- 
perature is  thus  obtained  and  another  specific-gravity  deter- 
mination made  of  the  material  at  this  elevated  temperature  as 
compared  with  water  at  the  same  temperature.  From  the 
known  K  of  water,  which  is  about  0.0002  per  °  C.,  the  specific 
gravity  of  the  material  at  the  elevated  temperature  is  then 
determined  as  compared  with  water  at  normal  temperature,  as 
follows: 

<;     r     Yo/^r  Sp.  Gr.  X°/X°C. 

Sp.  Gr.  X  /2S   C.  =  o_o 


The  coefficient  of  expansion  of  the  material  is  then  determined 
by  means  of  the  following  formula,  where  G  represents  the  spe- 


42    VALUE  OF  COEFFICIENT  OF  EXPANSION  DETERMINATION 

cific  gravity  at  normal  temperature  and  Gl  the  specific  gravity 
on  the  same  basis  at  the  observed  temperature. 

G-G1 


K  " 


G1   P- 


Value  of  Determination 

The  practical  value  of  the  coefficient  of  expansion  de- 
termination lies  in  its  application  to  volume  changes  which 
take  place  upon  heating  bituminous  materials,  especially 
where  the  material  is  purchased  or  used  upon  a  volume  basis, 
which  is  often  the  case.  In  the  vicinity  of  refineries,  bitu- 
minous materials  for  hot  -surf  ace  application  or  bituminous 
macadam  construction  are  not  uncommonly  delivered  at  the 
site  of  work  in  tank  wagons  or  tank  cars  at  a  temperature 
ready  to  apply.  As  the  purchase  price  and  rate  of  appli- 
cation are  based  upon  volumes  at  normal  temperature  or  at 
15.5°  C.,  it  is  necessary  to  know  the  coefficient  of  expansion  of 
the  material  in  order  to  compute  the  volume  at  such  tempera- 
ture. In  some  cases  an  arbitrary  figure  is  mutually  agreed  upon. 
Thus,  for  residual  petroleums  the  coefficient  of  expansion  is  often 
assumed  as  0.0004  per  °  F.  (0.00072  per  °  C.),  and  in  measuring 
hot  oils  a  deduction  of  0.4  per  cent  is  made  for  every  10°  F. 
above  60°  F.  (15.5°  C.),  which  is  commonly  taken  as  standard 
temperature.  The  general  formulas  for  finding  volumes  when 
K  is  known  are  as  follows: 


Comparatively  little  data  are  to  be  had  relative  to  the  coefficient 
of  expansion  of  the  various  bituminous  road  and  paving  mate- 
rials. In  general,  however,  for  a  given  type  of  material  the 
coefficient  of  expansion  decreases  as  the  specific  gravity  increases. 
Thus,  the  K  of  a  crude  petroleum  or  tar  is  greater  than  that  of 
its  residue  and  less  than  that  of  its  distillates.  From  the  data 
that  are  available,  it  appears  that  the  following  values  of  K  are 
reasonable  averages  for  the  types  of  materials  listed.  These 


CONSISTENCY    TESTS 


43 


figures  are,  however,  only  approximate,  and  in  certain  cases  are 
subject  to  considerable  variation. 

APPROXIMATE    COEFFICIENTS   OF   EXPANSION   OF    BITUMINOUS   MATERIALS 


Material 

K  per  °  C. 

-Kper°F. 

Gasoline  

0.00090 

0.00050 

Creosoting  oils 

00080 

OOO/M 

Fluid  residual  petroleums    

.00070 

.OOO^Q 

Fluid  tars  .                 

.00060 

.GOO"*"? 

Asphalt  cements 

00055 

00030 

Heavy  refined  tars             .           

.00055 

.00030 

CONSISTENCY  TESTS 

VISCOSITY 

Equipment: 

i  Engler  viscosimeter  complete  with  thermometers,  burner, 

and  rubber  tubing. 

i  zoo-cubic  centimeter  cylindrical  glass  graduate, 
i  stop-watch. 

Method. — The  viscosity  of  fluid  bituminous  road  materials  is 
determined  at  any  suitable  temperature,  most  commonly  by 
means  of  the  Engler  viscosimeter.  This  apparatus  is  shown  in 
Fig.  9,  and  may  be  described  as  follows:  a  is  a  brass  vessel  for 
holding  the  material  to  be  tested,  and  may  be  closed  by  the 
cover,  b.  To  the  conical  bottom  of  a  is  fitted  a  conical  outflow 
tube,  c,  exactly  20  millimeters  long,  with  a  diameter  at  the  top 
of  2.9  millimeters  and  at  the  bottom  of  2.8  millimeters.  This  tube 
can  be  closed  and  opened  by  the  pointed  hardwood  stopper,  d. 
Pointed  metal  projections  are  placed  on  the  inside  of  a  at  equal 
distances  from  the  bottom  and  serve  for  measuring  the  charge 
of  material,  which  is  240  cubic  centimeters.  The  thermometer 
€  is  used  to  ascertain  the  temperature  of  the  material  to  be 
tested.  The  vessel,  0,  is  surrounded  by  a  brass  jacket,  /,  which 
holds  the  material  used  as  .a  heating  bath,  either  water  or  cot- 
tonseed-oil, according  to  the  temperature  at  which  the  test  is 
to  be  made.  A  tripod,  g,  serves  as  a  support  for  the  apparatus, 
and  also  carries  a  ring  burner,  h,  by  means  of  which  the  bath 


44 


CONSISTENCY    TESTS 


is  directly  heated.  The  measuring  cylinder  of  100  cubic  centi- 
meters capacity,  which  is  sufficiently  accurate  for  work  with 
road  materials,  is  placed  directly  under  the  outflow  tube. 

As  viscosity  determinations  are  frequently  compared  with 
that  of  water  at  25°  C.,  the  apparatus  should  be  previously  cali- 
brated as  follows:  The  cup  and  outlet  tube  should  first  be  scru- 
pulously cleaned.  A  piece  of  soft  tissue  paper  is  convenient  for 


FIG.  9.     Engler  Viscosimeter 

cleaning  the  latter.  The  stopper  is  then  inserted  in  the  tube 
and  the  cup  filled  with  water  at  25°  C.  to  the  top  of  the  pro- 
jections. The  measuring  cylinder  should  be  placed  directly 
under  the  outflow  tube  so  that  the  material,  upon  flowing  out, 
will  not  touch  the  sides,  and  the  stopper  may  then  be  removed. 
The  time  required  both  for  50  and  100  cubic  centimeters  to  run 
out  should  be  ascertained  by  means  of  a  stop-watch,  and  the 
results  so  obtained  should  be  checked  a  number  of  times.  The 
time  required  for  50  cubic  centimeters  of  water  should  be  about 
ii  seconds  and  for  100  cubic  centimeters  about  22.8  seconds. 


VALUE    OF    VISCOSITY    DETERMINATION  45 

Bituminous  road  materials  are  tested  in  the  same  manner 
as  water,  and  the  temperature  at  which  the  test  is  made  is  con- 
trolled by  the  bath.  The  material  should  be  brought  to  the 
desired  temperature  and  maintained  there  for  at  least  three 
minutes  before  making  the  test.  The  results  are  expressed  as 
so-called  specific  viscosity  compared  with  water  at  25°  C.,  as 
follows: 

Specific  vis-    )  seconds  for  passage  of  given  volume  at  a  °C. 

cosity  at  a  °C.  )     ~  seconds  for  passage  of  same  volume  of  water  at  25  °C. 

It  should  be  noted  that  this  formula  does  not  give  the  actual 
specific  viscosity,  as  it  does  not  take  into  account  the  specific 
gravity  of  the  material  under  examination.  The  method  does, 
however,  tend  to  correct  and  place  upon  the  same  basis  different 
instruments. 

For  all  thin,  fluid  bituminous  road  materials  the  specific  vis- 
cosity is  determined  at  25°  C.  with  50  or  100  cubic  centimeters. 
Viscous  fluid  products  are  run  at  40°  C.  or  50°  C.  with  50  cubic 
centimeters,  and  very  viscous  products  at  100°  C.  or  over  with 
50  cubic  centimeters. 

Value  of  Determination 

While  the  Engler  viscosimeter  is  far  from  ideal  for  testing 
the  wide  range  of  liquid  bituminous  materials  used  in  highway 
engineering,  it  appears  to  be  the  most  generally  satisfactory 
instrument  for  this  purpose  that  has  yet  been  devised.  Unfor- 
tunately, it  is  not  well  adapted  for  deterrnining  the  specific  vis- 
cosity of  many  bituminous  materials  at  25°  C.  As,  for  the  dif- 
ferent types  of  materials,  viscosity  at  a  higher  temperature  is 
no  definite  measure  of  their  viscosity  at  25°  C.,  it  is  evident 
that  a  satisfactory  comparison  of  their  specific  viscosity  at 
normal  temperature  cannot  be  obtained  by  this  means.  As  a 
means  of  such  comparison  the  use  of  the  instrument  at  higher 
temperatures  is,  therefore,  limited  to  materials  of  the  same  type. 
The  interpretation  of  the  test,  except  with  reference  to  identi- 
fication and  control  of  a  given  type  and  grade  of  material,  is 
somewhat  complicated.  If,  however,  it  is  desired  to  apply  a 


46  VALUE    OF    VISCOSITY    DETERMINATION 

bituminous  material  at  a  given  temperature,  as,  for  instance, 
when  it  is  to  be  heated  in  a  tank  car  by  means  of  steam,  a  deter- 
mination of  its  viscosity  at  that  temperature  is  often  of  value. 
It  is  impossible  to  state  in  a  general  way  just  what  the  viscosity 
of  a  material  for  surface  application  should  be  during  applica- 
tion, as  this  is  largely  dependent  upon  the  type  of  distributer, 
its  spraying  nozzles,  and  its  speed  control.  It  is  a  fact,  how- 
ever, that  many  materials  sold  for  cold-surface  application  are 
entirely  too  viscous  at  normal  temperatures  for  uniform  distri- 
bution at  the  proper  rate  of  distribution,  but  what  may  be  a 
too  high  viscosity  for  one  type  of  material  may  not  be  too  high 
for  another  type.  As  a  measure  of  consistency  at  normal  tem- 
peratures, it  would  appear  advisable  to  limit  the  use  of  the 
Engler  viscosimeter  to  those  materials  intended  for  cold-surface 
application,  and  where  possible  to  utilize  some  other  consistency 
test  for  indicating  the  consistency  at  normal  temperature  of 
those  materials  which  have  to  be  heated  before  application.  In 
fact,  a  viscosity  determination  is  seldom  made  upon  a  material 
whose  consistency  at  normal  temperature  may  be  made  with 
some  other  consistency  test. 

In  general,  at  normal  temperatures,  fluid  distillates  show  a 
much  lower  specific  viscosity  than  do  fluid  petroleum  or  tar 
residuums.  Crude  and  dehydrated  petroleums  and  tars  vary 
greatly  in  viscosity.  Among  the  petroleums,  however,  those  of 
the  asphaltic  type  are  usually  much  more  viscous  than  the  paraf- 
fin or  semi-asphaltic  type.  Among  the  tars,  the  viscosity  of 
crude  water-gas  tar  is  lowest  and  gas-house  coal  tars  from  hori- 
zontal retorts  the  highest.  For  a  given  type  of  fluid  residual 
petroleum  or  tar  produced  by  fractional  distillation,  the  specific 
viscosity  increases  with  the  specific  gravity  and  decreases  with 
the  coefficient  of  expansion.  As  regards  fluid  residuums  which 
are  subjected  to  the  blowing  process,  however,  the  viscosity 
may  be  greatly  increased  without  markedly  increasing  the  specific 
gravity  of  the  residuum.  The  viscosity  of  all  bituminous  mate- 
rials decreases  as  their  temperature  increases.  In  any  bitumi- 
nous material  the  presence  of  finely  divided  non-bituminous 
impurities'  held  in  suspension  will  often  greatly  increase  the  vis- 


FLOAT    TEST 


cosity  of  the  material,  although  the  actual  viscosity  of  its  pure 
bitumen  may  be  low. 

The  viscosity  test  is  largely  used  as  a  control  test  in  the 
manufacture  of  liquid  bituminous  materials  of  interest  in  high- 
way engineering. 

FLOAT  TEST 

Equipment: 

1  aluminum  float  or  saucer.     (Fig.  ioa.) 

2  conical  brass  collars.     (Fig.  lob.) 
2  i -quart  tin  cups,  seamless. 

2  chemical  thermometers  reading  from  — 10°  C.  to  110°  C. 

i  iron  tripod. 

i  Bunsen  burner  and  rubber  tubing. 

i  burette  clamp  and  support. 

i  large  metal  kitchen  spoon. 

i  steel  spatula  or  kitchen  knife. 

i  brass  plate  about  six  inches  square  and  one-eighth  inch 

thick. 

i  stop-watch. 

Method. — The  New  York  Testing  Laboratory  float  apparatus 
consists  of  two  parts,  an  aluminum  float  or  saucer  (Fig.  ioa), 


FIG.  10.     New  York  Testing  Laboratory  Float  Apparatus 


48  FLOAT    TEST 

and  a  conical  brass  collar  (Fig.  io&).  The  two  parts  are  made 
separately,  so  that  one  float  may  be  used  with  a  number  of 
brass  collars. 

In  making  the  test,  the  brass  collar  is  placed  with  the  small 
end  down  on  the  brass  plate,  which  has  been  previously  amal- 
gamated with  mercury  by  first  rubbing  it  with  a  dilute  solu- 
tion of  mercuric  chloride  or  nitrate  and  then  with  mercury. 
A  small  quantity  of  the  material  to  be  tested  is  heated  in  the 
metal  spoon  until  quite  fluid,  with  care  that  it  suffers  no  appre- 
ciable loss  by  volatilization  and  that  it  is  kept  free  from  air- 
bubbles.  It  is  then  poured  into  the  collar  in  a  thin  stream  until 
slightly  more  than  level  with  the  top.  The  surplus  may  be  re- 
moved, after  the  material  has  cooled  to  room  temperature,  by 
means  of  a  spatula  or  steel  knife  which  has  been  slightly  heated. 
The  collar  and  plate  are  then  placed  in  one  of  the  tin  cups  con- 
taining ice  water  maintained  at  5°  C.,  and  left  in  this  bath  for 
at  least  15  minutes.  Meanwhile  the  other  cup  is  filled  about 
three-fourths  full  of  water  and  placed  on  the  tripod,  and  the 
water  is  heated  to  any  desired  temperature  at  which  the  test 
is  to  be  made.  This  temperature  should  be  accurately  main- 
tained, and  should  at  no  time  throughout  the  entire  test  be 
allowed  to  vary  more  than  one-half  a  degree  Centigrade  from 
the  temperature  selected.  After  the  material  to  be  tested  has 
been  kept  in  the  ice  water  for  at  least  15  minutes,  the  collar 
with  its  contents  is  removed  from  the  plate  and  screwed  into 
the  aluminum  float,  which  is  then  immediately  floated  in  the 
warmed  bath.  As  the  plug  of  bituminous  material  becomes 
warm  and  fluid,  it  is  gradually  forced  upward  and  out  of  the 
collar  until  water  gains  entrance  to  the  saucer  and  causes  it 
to  sink. 

The  tune  in  seconds  between  placing  the  apparatus  on  the 
water  and  when  the  water  breaks  through  the  bitumen  is  deter- 
mined by  means  of  a  stop-watch  and  is  taken  as  a  measure 
of  the  consistency  of  the  material  under  examination. 

The  float  test  is  preferably  made  at  50°  C.  Very  soft  prod- 
ucts which  show  a  test  at  this  temperature  of  only  a  few  sec- 
onds, however,  may  be  advantageously  tested  at  a  lower  tern- 


VALUE    OF    FLOAT    TEST  49 

perature,  such  as  32°  C.  If  the  test  at  50°  C.  requires  over  four 
or  five  minutes,  it  is  sometimes  made  at  65°  C.,  and  if  the  melting 
point  of  the  material  is  high,  the  test  is  run  at  100°  C. 

Value  of  Test 

The  float  test  has  sometimes  been  called  a  viscosity  test. 
In  some  respects  it  is  a  measure  of  the  resistance  to  flow  pos- 
sessed by  the  material,  but  it  differs  from  the  average  viscos- 
ity test  mainly  in  the  fact  that  the  temperature  of  the  material 
itself  is  constantly  changing  throughout  the  test.  It  cannot  be 
used  with  very  fluid  materials,  but  for  the  very  viscous  fluids 
which  become  almost  semisolid  at  the  temperature  of  ice  water 
and  for  many  normally  semisolid  products  it  serves  as  a  very 
satisfactory  measure  of  consistency  at  normal  temperature, 
although  the  test  itself  is  conducted  at  a  higher  temperature. 
Providing  the  temperature  of  the  test  is  the  same,  it  serves  rea- 
sonably well  as  a  basis  of  comparing  the  consistency  at  normal 
temperature  of  both  straight  residual  and  fluxed  products  of 
the  same  type.  It  has  the  distinct  advantage  over  the  viscos- 
ity test  of  being  less  susceptible  to  the  influence  of  inert,  finely 
divided  suspended  material  which  may  be  present,  because  of 
the  comparatively  large  orifice  of  the  collar.  For  this  reason 
it  more  nearly  represents  the  consistency  of  the  actual  bitumen, 
and  is  particularly  well  adapted  for  detenriining  the  consistency 
of  tars,  irrespective  of  their  free  carbon  content.  In  this  con- 
nection it  is  used  to  a  considerable  extent  as  a  control  test  in 
the  manufacture  of  heavy  residual  tars.  It  is  not  as  well  adapted 
for  testing  the  semisolid  blown-oil  products  which  conduct  heat 
so  slowly  that  only  the  surface  in  contact  with  the  collar  becomes 
fluid  before  the  entire  plug  of  semisolid  material  is  forced  out. 
For  a  given  type  of  residual  material  the  float  test  at  a  given 
temperature  decreases  with  the  specific  gravity.  For  any  mate- 
rial it  naturally  decreases  as  the  temperature  of  the  test  is  in- 
creased. For  fluid  products  which  harden  rapidly  upon  expos- 
ure, such  as  cut-backs,  the  float  test  is  useful  as  a  means  of 
determining  the  consistency  of  the  residue  from  the  volatiliza- 


50  PENETRATION    TEST 

tion  test,  especially  the  soft  residues  which  cannot  well  be  sub- 
jected to  the  penetration  test. 

PENETRATION  TEST 

Equipment: 

i  penetrometer  complete,   with  a  seconds  pendulum  or 

metronome.     (Figs,  n  and  12.) 
i  tin  box,  approximately  5.5  centimeters  in  diameter  by 

3.5  centimeters  in  height, 
i  large  metal  kitchen  spoon, 
i  steel  spatula  or  kitchen  knife, 
i  glass  penetration  dish,  approximately  10  centimeters  in 

diameter  by  6  centimeters  high, 
i  enamelware   dish,  approximately  3   inches   deep  and  9 

inches  in  diameter. 

i  chemical  thermometer  reading  from  — 10°  C.  to  110°  C. 
Method. — The  object  of  the  penetration  test  is  to  ascertain 
the  consistency  of  the  material  under  examination  by  determin- 
ing the  distance  a  weighted  needle  will  penetrate  into  it  at  a 
given  temperature  under  known  conditions  of  time  and  load. 
A  standard  needle  is  employed  for  this  purpose,  and  this  needle 
is  usually  weighted  with  100  grams.  The  depth  of  penetration 
is  most  commonly  determined  upon  the  bitumen  maintained 
at  25°  C.,  while  the  load  is  applied  for  five  seconds. 

The  standard  needle  is  made  from  round,  polished,  annealed- 
steel  drill-rod  having  a  diameter  of  from  0.0405  to  0.0410  inches. 
The  rod  is  tapered  to  a  sharp  point  at  one  end,  with  the  taper 
extending  back  one-fourth  inch.  It  is  then  highly  polished, 
tempered,  and  again  polished  with  jewelers'  rouge.  The  fin- 
ished needle  is  from  i^  to  2  inches  in  length  and  exactly  0.040 
inch  in  diameter.  This  needle  gives  the  same  results  as  the 
old  standard  No.  2  cambric  needle,  and  possesses  the  advantage 
that  it  can  be  exactly  duplicated  and  accurately  described. 

There  are  a  number  of  penetration  machines  in  common  use 
which  employ  the  same  standards  of  test,  and  therefore  give 
practically  equivalent  results.  Among  them  may  be  mentioned 
the  Dow,  the  New  York  Testing  Laboratory,  and  the  Hum- 


PENETRATION    TEST 


51 


boldt  penetrometers.  The  Dow  machine,  shown  in  Fig.  n, 
consists  of  a  standard  needle,  a,  inserted  in  a  short  brass  rod, 
which  is  held  in  the  aluminum  rod,  bt  by  a  binding  screw.  The 
aluminum  rod  is  secured  in  a  framework  so  weighted  and  bal- 
anced that,  when  it  is  supported  on  the  point  of  the  needle,  the 
framework  and  rod  will  stand  in  an  upright  position,  allowing 


FIG.  ii.     Dow  Penetration  Machine 

the  needle  to  penetrate  perpendicularly  without  the  aid  of  a 
support. 

The  frame,  aluminum  rod,  and  needle  weigh  100  grams  with 
the  weight  c  on  the  bottom  of  the  frame,  while  without  the  weight 
they  weigh  50  grams.  Fig.  n  shows  the  needle  and  weighted 
frame,  together  with  side  and  front  views  of  the  entire  apparatus, 
put  together  and  ready  for  making  a  penetration.  The  shelf 
for  the  sample  is  marked  d;  e  is  the  clamp  to  hold  the  alumi- 
num rod  until  it  is  desired  to  make  a  test,  and  /  is  a  button 
which,  when  pressed,  opens  the  clamp.  By  turning  this  button 
while  the  clamp  is  being  held  open,  it  will  lock  and  keep  the 
clamp  from  closing  until  unlocked.  The  device  for  measuring 


52 


PENETRATION    TEST 


the  distance  penetrated  by  the  needle  consists  of  a  rack,  with 
a  foot,  g.  The  movement  of  this  rack  turns  a  pinion,  to  which 
is  attached  the  hand  which  indicates  on  the  dial,  h,  the  vertical 
distance  covered  by  the  rack.  One  division  of  the  dial  corre- 
sponds to  a  movement  of  o.oi  centimeter  by  the  rack.  The  rack 
may  be  raised  or  lowered  by  moving  the  counterweight,  i9  up 
or  down.  The  tin  box  containing  the  sample  to  be  tested  is 


FIG.  12.     New  York  Testing  Laboratory  Penetrometer 

marked  k;  this  is  submerged  in  water  contained  in  the  glass 
cup  in  order  to  maintain  a  constant  temperature. 

Another  type  of  machine  known  as  the  New  York  Testing 
Laboratory  penetrometer,  based  upon  the  same  general  prin- 
ciple and  using  the  same  standards,  is  shown  in  Fig.  12. 
Both  machines  give  practically  the  same  results  if  operated 
under  the  same  conditions,  and  it  is  therefore  considered  unnec- 
essary to  include  a  description  of  the  latter. 

A  cup  suitable  for  holding  the  box  containing  the  test  sample 
during  penetration  is  conveniently  made  from  a  glass  crystal- 
lizing dish  10  centimeters  in  diameter,  with  straight  sides  about 
6  centimeters  high.  Three  right  triangles  with  right-angle  sides, 
i  and  5  centimeters,  respectively,  are  cut  from  i/i6-inch  sheet 


PENETRATION    TEST  53 

metal.  Some  solid  bitumen  is  melted  in  the  bottom  of  the  dish, 
forming  a  layer  about  y%  inch  thick,  into  which  the  triangles 
are  placed,  resting  on  the  side  five  centimeters  long.  Their 
apexes  should  meet  at  the  center,  with  their  short  sides  dividing 
the  circumference  of  the  dish  into  three  equal  arcs.  When  the 
bitumen  has  hardened,  the  triangles  give  a  firm  support  for 
circular  boxes,  and  the  possibility  of  any  rocking  motion  and 
consequent  faulty  results  is  avoided. 

The  penetration  test  is  made  as  follows:  A  sample  of  the 
material  to  be  tested  is  first  warmed  sufficiently  to  flow,  and 
poured  into]  the  box.*  The  box  and  contents,  after  cooling 
for  one  hour  at  room  temperature,  are  immersed  in  water  main- 
tained at  the  temperature  at  which  the  test  is  to  be  made,  and 
allowed  to  remain  immersed  for  one  hour.  The  sample  in  the 
tin  box  should  now  be  placed  in  the  glass  cup  and  removed 
in  it,  covered  with  as  much  water  as  convenient  without  spill- 
ing, to  the  shelf  d.  The  brass  rod  with  the  needle  is  inserted  into 
b  and  secured  by  tightening  the  binding  screw.  The  rod  is 
lowered  until  the  point  of  the  needle  almost  touches  the  sur- 
face of  the  sample;  then  by  grasping  the  frame  with  both 
hands  it  is  cautiously  pulled  down  until  the  needle  just  comes 
in  contact  with  the  surface  of  the  sample.  This  can  be  seen 
best  by  having  a  light  so  situated  that,  upon  looking  through 
the  sides  of  the  glass  cup,  the  needle  will  be  reflected  from  the 
surface  of  the  sample.  After  thus  setting  the  needle,  the  counter- 
weight is  slowly  raised  until  the  foot  of  the  rack  rests  on  the 
head  of  the  rod  and  a  reading  of  the  dial  taken.  The  clamp 
is  then  opened  wide  by  pressing  the  button  and  held  in  this 
position  for  exactly  five  seconds,  as  determined  by  the  pendu- 
lum or  metronome.  The  clamp  is  then  released,  the  rack  lowered 
until  it  rests  on  the  rod,  and  the  difference  between  the  first  and 
second  readings  of  the  dial  in  hundredths  of  a  centimeter  is 
taken  as  the  distance  penetrated  by  the  needle. 

Owing  to  the  susceptibility  of  certain  bitumens  to  slight 
changes  in  temperature,  the  water  bath  should  be  accurately 

*  American  Can  Company's  Gill  style  ointment-box,  deep  pattern,  3-oz.  capacity,  meets 
the  requirements. 


54  VALUE    OF    PENETRATION    TEST 

maintained  at  the  desired  temperature,  both  before  and  during 
the  test  to  within  0.1°  C.,  and,  when  the  room  temperature  dif- 
fers greatly  from  that  of  the  bath,  the  water  in  the  glass  cup 
should  be  renewed  after  each  test.  An  average  of  from  three 
to  five  tests,  which  should  not  differ  more  than  four  points 
between  maximum  and  minimum,  is  taken  as  the  penetration 
of  the  sample.  The  tests  should  be  made  at  points  on  the 
surface  of  the  sample  not  less  than  one  centimeter  from  the 
side  of  the  container  and  not  less  than  one  centimeter  apart. 

The  needle  should  be  removed  and  thoroughly  cleaned  by 
wiping  with  a  dry  cloth,  after  which  it  is  ready  for  another 
test.  The  point  of  the  needle  should  be  examined  from  time 
to  time  with  a  magnifying  glass  to  see  that  it  is  not  injured 
in  any  way.  If  it  is  found  defective  it  may  be  removed  by 
heating  the  brass  rod  and  withdrawing  with  pliers.  A  new 
needle  may  then  be  inserted  in  the  heated  brass  rod.  and  held 
firmly  in  place  by  a  drop  of  soft  solder. 

While  the  standard  conditions  under  which  this  test  is  made 
call  for  a  loo-gram  load  applied  for  five  seconds  on  the  mate- 
rial maintained  at  a  temperature  of  25°  C.,  it  is  sometimes  desir- 
able, when  very  soft  materials  are  tested,  to  make  the  test 
with  a  5o-gram  weight.  In  order  to  ascertain  how  susceptible 
a  material  may  be  to  temperature  changes,  tests  may  be  made 
at  any  other  desired  temperatures,  preferably  o°  C.  with  a  200- 
gram  weight  for  one  minute,  and  at  46°  C.  with  a  50-gram 
weight  for  five  seconds.  When  the  test  is  made  at  o°  C.  the 
sample  should  be  immersed  in  brine. 

In  all  cases  the  results  of  tests  should  be  reported  in  hun- 
dredths  of  a  centimeter,  as  follows,  showing  all  the  conditions 
in  order  that  no  misinterpretation  of  results  may  occur: 

Penetration  ( —  seconds.  —  grams  at  — °  C.)  =  — . 

Value  of  Test 

The  penetration  test  is  most  commonly  used  in  connection 
with  asphalts  and  asphalt  cements,  although  it  is  sometimes 
used  in  testing  the  harder- tar  residuums.  For  the  manufacture 


VALUE    OF    PENETRATION    TEST  55 

of  the  former  type  of  materials  it  serves  as  a  control  test.  These 
materials  are  commonly  graded  by  their  penetration  at  25°  C., 
and  in  all  cases  where  the  term  "penetration"  is  used  without 
other  qualification  it  is  understood  that  the  temperature  of  25° C. 
is  implied  and  that  the  test  is  made  with  a  standard  needle  under 
a  load  of  100  grams  applied  for  five  seconds.  The  test  is  not  as 
useful  as  a  means  of  control  or  in  grading  the  tar  residuums 
used  in  highway  engineering  for  the  reason  that  most  of  these 
residuums  are  quite  soft,  and,  as  their  surface  tension  is  very 
high,  they  press  out  or  deform  under  the  loaded  needle  much 
more  than  do  the  asphalt  cements  commonly  used.  The  true 
penetration  is  not,  therefore,  as  accurately  recorded,  the  result 
obtained  representing  to  a  very  considerable  extent  the  measure 
of  surface  deformation  rather  than  actual  penetration.  In  gen- 
eral, the  more  susceptible  the  bituminous  material  is  to  tem- 
perature changes  the  greater  its  surface  deformation  under  the 
loaded  needle.  Susceptibility  to  temperature  changes  may  be 
determined  by  means  of  the  penetration  test  made  at  the  tem- 
peratures of  o°  or  4°,  25°,  and  46°  C.,  which  serve  as  approxi- 
mate minimum  average  and  maximum  temperatures  of  the  pave- 
ment proper  in  which  the  material  may  be  incorporated. 

In  the  manufacture  of  bituminous  materials  the  semisolid 
residues  produced  by  distillation  become  harder  and.  harder  as 
distillation  progresses,  or,  hi  other  words,  the  penetration  of 
these  residues  decreases  with  distillation.  For  a  given  type 
of  residue  the  penetration,  therefore,  decreases  as  the  specific 
gravity  increases.'  This  relation  is  not,  however,  so  marked 
in  the  case  of  blown  products,  which  may  decrease  markedly 
in  penetration  with  very  slight  change  in  specific  gravity  as  the 
blowing  process  progresses.  In  comparing  different  types  of 
materials  there  is  no  definite  relation  between  penetration  and 
specific  gravity.  Thus  an  asphalt  cement  of  a  given  penetra- 
tion produced  by  straight  distillation  of  a  California  petroleum 
will  usually  show  a  much  lower  specific  gravity  than  will  one 
of  the  same  penetration  from  a  Mexican  petroleum  or  by  flux- 
ing a  native  asphalt.  Highly  blown  asphalt  cements  may  usu- 
ally be  identified  by  a  very  low  specific  gravity  as  compared 


56  MELTING    OR    SOFTENING    POINT    TESTS 

with  residual  and  fluxed  native  asphalts  of  the  same  penetration. 
Thus  the  penetration  test,  while  practically  valueless  alone  as 
a  means  of  identification,  owing  to  the  fact  that  almost  any 
type  of  material  can  be  manufactured  at  any  desired  penetra- 
tion, may  be  a  valuable  aid  to  identification  when  considered 
in  connection  with  the  specific  gravity  of  the  material. 

Besides  being  applied  to  the  original  material  the  penetra- 
tion test  is  ordinarily  made  where  possible  upon  the  residue 
from  the  volatilization  test  to  determine  what  changes  in  con- 
sistency have  been  produced  by  volatilization.  It  is  also  of 
great  importance  in  the  plant  inspection  of  asphalt  cements 
prepared  at  the  paving  plant  by  fluxing  refined  asphalts.  When 
made  at  various  temperatures  it  may  be  used  to  determine  the 
susceptibility  of  a  material  to  temperature  changes. 

MELTING   OR   SOFTENING-POINT   TESTS 

~     . .  Cube  Method 

Equipment: 

i  iron  tripod. 

i  Bunsen  burner  ana  rubber  tubing. 

i  piece  of  wire  gauze  10  centimeters  square. 

i  8oo-cubic  centimeter  Jena  glass  beaker,  low  form.     (Fig. 

13*0 

i  4oo-cubic  centimeter  Jena  giass  beaker,  tall  without  lip. 

(Fig.  136.) 

i  iron  ring  support  (ring  7.5  centimeters  in  diameter)  and 
burette  clamp.  (Fig.  136.) 

i  metal  cover.     (Fig.  13^.) 

i  object  glass. 

i  piece  of  wire  (No.  12  Brown  &  Sharpe  gauge)  20  centi- 
meters in  length,  bent.  (Fig.  130.) 

i  chemical  thermometer  reading  from  o°  C.  to  250°  C. 

i  cubical  brass  mold.     (Fig.  i$f.) 

i  brass  plate  about  six  inches  square  and  y&rf-  thick. 

i  large  metal  kitchen  spoon. 

i  steel  spatula  or  kitchen  knife. 


CUBE    METHOD 


57 


The  material  under  examination  is  first  melted  in  the  spoon 
by  the  gentle  application  of  heat  until  sufficiently  fluid  to  pour 
readily.  Care  must  be  taken  that  it  suffers  no  appreciable  loss 
by  volatilization.  It  is  then  poured  into  the  >^-inch  brass 
cubical  mold,  which  has  been  amalgamated  with  mercury  and 
which  is  placed  on  an  amalgamated  brass  plate.  The  brass 
may  be  amalgamated  by  washing  it  first  with  a  dilute  solution 
of  mercuric  chloride  or  nitrate,  after  which  the  mercury  is 


FIG.  13.     Melting-Point  Apparatus — Cube  Method 

rubbed  into  the  surface.  By  this  means  the  bitumen  is,  to 
a  considerable  extent,  prevented  from  sticking  to  the  sides  of 
the  mold.  The  hot  material  should  slightly  more  than  fill  the 
mold  and,  when  cooled,  the  excess  may  be  cut  off  with  a  hot 
spatula  or  knife. 

After  cooling  to  room  temperature,  the  mold  is  placed  in  a 
bath  maintained  at  25°  C.  for  one  half -hour.  The  cube  is  then 
removed  and  fastened  upon  the  lower  arm  of  a  No.  12  wire 
(Brown  &  Sharpe  gauge),  bent  at  right  angles  and  suspended 
beside  a  thermometer  in  a  covered  Jena  glass  beaker  of  400 
cubic  centimeters  capacity,  which  is  placed  in  a  water  bath, 
or,  for  high  temperatures,  a  cottonseed-oil  bath.  The  wire 


58  RING    AND    BALL    METHOD 

should  be  passed  through  the  center  of  two  opposite  faces  of  the 
cube,  which  is  suspended  with  its  base  i  inch  above  the  bottom 
of  the  beaker.  The  water  or  oil  bath  consists  of  an  8oo-cubic 
centimeter  low-form  Jena  glass  beaker  suitably  mounted  for 
the  application  of  heat  from  below.  The  beaker  in  which  the 
cube  is  suspended  is  of  the  tall-form  Jena  type  without  lip. 
The  metal  cover  has  two  openings  as  shown  in  Fig.  13^.  A  cork, 
through  which  passes  the  upper  arm  of  the  wire,  is  inserted  in 
one  hole  and  the  thermometer  in  the  other.  The  bulb  of  the 
thermometer  should  r^e  just  level  with  the  cube  and  at  an  equal 
distance  from  the  side  of  the  beaker.  In  order  that  a  reading 
of  the  thermometer  may  be  made,  if  necessary,  at  the  point 
which  passes  through  the  cover,  the  hole  is  made  triangular 
in  shape  and  covered  with  an  ordinary  object  glass  through 
which  the  stem  of  the  thermometer  may  be  seen.  Readings 
made  through  this  glass  should  be  corrected  for  the  angle  of 
observation,  which  may  be  made  constant  by  always  sighting 
from  the  front  edge  of  the  opening  at  any  given  point  on  the 
stem  of  the  thermometer  below  the  cover. 

After  the  test  specimen  has  been  placed  in  the  apparatus, 
the  liquid  in  the  outer  vessel  is  heated  in  such  a  manner  that 
the  thermometer  registers  an  increase  of  5°  C.  per  minute. 
The  temperature  at  which  the  bitumen  touches  a  piece  of  paper 
placed  in  the  bottom  of  the  beaker  is  taken  as  the  melting 
point.  Determinations  made  in  the  manner  described  should 
not  vary  more  than  two  degrees  for  different  tests  of  the  same 
material.  At  the  beginning  of  this  test  the  temperature  of 
both  bitumen  and  bath  should  be  approximately  25°  C.  For 
tar  products  the  test  is  sometimes  run  with  the  cube  suspended 
directly  in  water,  in  which  case  only  the  smaller  beaker  is 
required. 

Ring  and  Ball  Method 
Equipment: 

i  iron  tripod. 

i  Bunsen  burner  and  rubber  tubing. 

i  piece  wire  gauze  10  centimeters  square  with  asbestos 
center. 


RING    AND    BALL    METHOD 


59 


i  6oo-cubic  centimeter  beaker. 

i  ring  attached  to  heavy  wire. 

i  steel  ball. 

i  cork. 

i  iron  stand  with  burette  clamp. 

i  chemical  thermometer  reading  from  o°  C.  to  250°  C. 

i  brass  plate  about  six  inches  square  and  y£"  thick. 

i  large  metal  kitchen  spoon. 

i  steel  spatula  or  kitchen  knife. 

Method. — This  method  for  other  than  tar  products  has  been 
recommended  to  the  American  Society  for  Testing  Materials 
for  adoption  as  standard  by  Committee  D~4.  It  is,  however, 
here  described  somewhat  more  in  detail  than  in  the  Committee's 
recommendations. 

The  mold  consists  of  a  brass  ring  ^i  inch  in  diameter  and 
y^  inch  thick,  with  a  wall  3/3*  inch  thick.  The  ring  is  fastened 
to  a  stout  wire  in  a  horizontal 
position  at  right  angles  to  the 
wire.  A  steel  ball  ^  inch  in 
diameter  and  weighing  between 
3.45  and  3.50  grams  is  also 
required.  When  ready  for  test 
the  apparatus  is  set  up  as  shown 
in  Fig.  14  upon  the  metal  tri- 
pod, the  ring  being  suspended 
in  a  horizontal  position  inside 
and  one  inch  above  the  bottom 
of  the  beaker,  which  should 
contain  approximately  400  cubic 
centimeters  of  water  at  5°  C. 

The  material  under  examina- 
tion is  first  melted  in  the  spoon 
by  the  gentle  application  of  heat 
until  sufficiently  fluid  to  pour 
readily.  Care  must  be  taken 
that  it  suffers  no  appreciable  loss  by  volatilization. 


FIG.  14.    Melting- Point  Apparatus 
— Ring  and  Ball  Method 


It    is 


then  poured  into  the  ring,  which  is  placed  upon  an  amalga- 


60  VALUE    OF    MELTING-POINT    TEST 

mated  brass  plate.  The  hot  material  should  slightly  more 
than  fill  the  ring,  and  when  cooled  the  excess  may  be  cut 
off  with  a  hot  spatula  or  knife.  The  ball  is  next  placed 
upon  the  surface  of  the  material  in  the  center  of  the  ring  and 
the  whole  suspended  in  the  beaker  as  above  described, 
with  the  thermometer  bulb  within  J^  inch  of  the  sample  and 
at  the  same  level.  Heat  is  then  applied  uniformly  to  the 
bottom  of  the  beaker  in  quantity  sufficient  to  raise  the  tem- 
perature of  the  water  5°  C.  per  minute.  The  temperature  is 
recorded  at  the  start  of  the  test  and  every  minute  thereafter, 
as  the  rate  of  heating  is  a  very  important  factor.  The  melting 
or  softening  point  is  that  temperature  at  which  the  material 
first  touches  the  bottom  of  the  beaker,  Successive  tests  should 
average  within  3°  C.  For  melting  points  above  95°  C.  a  glycerine 
bath  should  be  used  instead  of  water. 

Value  of  Melting-Point  Test 

As  bituminous  materials  are  not  definite  individual  com- 
.  pounds  and  as  those  which  are  ordinarily  termed  solids  are  not 
true  solids  but  practically  solid  solutions,  it  follows  that  they 
can  have  no  true  melting  point.  In  other  words,  bitumen  which 
may  be  hard  and  brittle  at  normal  temperature  will,  when 
heated,  gradually  become  softer  and  softer  until  it  flows  readily 
and  no  critical  temperature  can  be  observed  for  its  change 
from  apparent  solid  to  liquid  form.  Any  method  of  determin- 
ing the  so-called  melting  point  of  bituminous  materials  is  there- 
fore purely  arbitrary  and  gives  purely  arbitrary  results.  For 
this  reason  different  methods  give  different  results  with  the 
same  material,  and  in  reporting  results  or  preparing  specifica- 
tions it  is  therefore  necessary  to  indicate  ,the  method  used  or 
to  be  used.  No  absolutely  definite  relation  applicable  to  bitu- 
minous materials  in  general  has  as  yet  been  found  to  exist 
between  the  cube  method  and  the  ring  and  ball  method. 

A  melting-point  test  may  be  made  upon  any  type  of  bitu- 
men which  is  sufficiently  solid  to  hold  its  shape  for  some  time 
under  conditions  maintained  at  the  beginning  of  the  test.  In 


DUCTILITY  61 

x 

the  manufacture  of  tar  pitches  and  blown  petroleums  or  as- 
phalts it  is  often  used  as  a  control  test,  and  such  materials  are 
sometimes  graded  by  their  melting  point.  As  different  manu- 
facturers use  different  methods,  however,  a  stated  melting  point 
has  no  particular  significance  unless  the  method  is  known.  In 
general,  as  the  distillation  of  a  bituminous  material  progresses, 
the  melting  point  of  the  semisolid  and  solid  residues  increases. 
For  straight-distilled  products  of  a  given  type,  therefore,  the 
melting  point  increases  with  an  increase  in  specific  gravity  and 
an  increase  in  float  test  or  a  decrease  in  penetration  at  any 
given  temperature.  If,  however,  the  blowing  process  is  used, 
particularly  with  petroleum  products,  an  increase  in  melting 
point  may  be  obtained  with  a  very  slight  increase  in  specific 
gravity  and  decrease  in  penetration  as  compared  with  the  accom- 
panying changes  in  specific  gravity  and  penetration  had  the 
product  been  distilled  to  the  same  melting  point.  By  properly 
manipulating  the  distilling  and  blowing  processes,  various  com- 
binations of  melting  point  and  penetration  may  be  secured 
from  the  same  original  material.  For  a  given  penetration  at 
normal  temperature,  high  melting-point  materials  are  as  a  rule 
less  susceptible  to  the  ordinary  temperature  changes  than  are 
low  melting-point  materials. 

In  connection  with  the  specific  gravity  and  penetration  tests 
the  melting-point  test  may  serve  as  a  means  not  only  of  identi- 
fying a  material  but  also  of  ascertaining  its  method  of  manu- 
facture. Besides  being  applied  to  the  original  material  the 
melting-point  test  may  be  made  upon  the  residue  from  the 
distillation  test  of  tars,  for  the  purpose  of  identifying  cut-back 
hard  pitches.  It  is  seldom  made  upon  the  residue  from  the 
volatilization  test. 

DUCTILITY 

Equipment: 

i  ductility  machine  complete  with  briquet  molds. 

i  large  metal  kitchen  spoon. 

i  steel  spatula  or  kitchen  knife. 

i  brass  plate  about  6  inches  square  and  y%  inch  thick. 

i  chemical  thermometer  reading  from  — 10°  to  110°  C. 


62 


DUCTILITY 


Method. — Like  the  penetration  test,  there  are  a  number  of 
machines  in  common  use  for  determining  the  ductility  of  bitu- 
minous materials  which  employ  the  same  standards,  and  there- 
fore give  practically  equivalent  results.  The  test  as  ordinarily 
applied  to  asphalt  cements  was  devised  by  Dow,  whose  machine 
is  perhaps  the  best  known.  Other  types  in  common  use  are  the 
Kirschbraun  machine  and  the  Chew  machine,  which  latter  is 
shown  in  Fig.  15.  In  all  of  these  machines  a  test  specimen  of 
the  same  standard  shape  and  size  is  tested  by  pulling  it  apart 


FIG.  15.     Chew  Ductility  Machine 

at  a  given  rate  and  noting  the  distance  that  it  stretches  before 
breaking.  In  some  cases  the  pulling  is  accomplished  by  means 
of  a  gear  operated  by  a  hand  wheel,  but  a  motor  drive  such  as 
shown  in  the  figure  is  to  be  preferred,  as  it  insures  greater  uni- 
formity in  the  rate  of  pull. 
The  Chew  machine  also  has  an 
automatic  device  for  indicating 
the  rate  of  pull. 

The  test  substantially  as 
recommended  in  1915  by  "The 
Special  Committee  on  Road 
Materials  of  The  American  So- 
ciety of  Civil  Engineers"  is  as 
follows: 

The  briquet  mold  shown  in  Fig.  16  is  made  of  brass  and 
consists  of  four  parts,  two  end  clips  (a  a)  and  two  side  pieces 
(bb).  When  these  parts  are  properly  fitted  together  they 
should  cast  a  briquet  i  centimeter  in  thickness  throughout 


HE 


FlG.  1 6.     Briquet  Mold  for 
Ductility  Test 


DUCTILITY  63 

its  entire  length.  The  distance  between  the  end  clips  should 
be  3  centimeters,  the  width  at  the  mouth  of  the  clips  should 
be  2  centimeters,  and  the  width  at  the  niinimum  cross-section, 
half-way  between  the  clips,  should  be  i  centimeter. 

When  casting  a  briquet  the  inside  faces  of  the  two  side 
pieces  are  first  thoroughly  amalgamated  with  mercury.  The 
mold  is  then  put  together  and  placed  upon  an  amalgamated 
brass  plate.  The  material  to  be  tested  is  next  heated  in  a  metal 
spoon  until  quite  fluid,  with  care  that  it  suffers  no  appreciable 
loss  by  volatilization.  It  is  then  poured  into  the  mold  until 
slightly  more  than  level  with  the  top.  The  surplus  may  be 
removed,  after  the  material  has  cooled  to  room  temperature, 
by  means  of  a  spatula  or  steel  knife  which  has  been  slightly 
heated.  The  two  side  pieces  of  the  mold  are  next  removed, 
leaving  the  briquet  of  material  held  at  each  end  by  the  ends 
of  the  mold,  which  now  play  the  part  of  clips.  In  case  the 
material  tends  to  adhere  to  the  sides  of  the  mold  their  removal 
may  be  facilitated  by  immersing  the  material  for  a  few  moments 
in  cold  water. 

The  briquet  with  clips  attached  is  then  placed  in  water 
which  is  carefully  maintained  at  25°  C.  and  allowed  to  remain 
for  not  less  than  thirty  minutes.  It  is  then  transferred  to  the 
ductility  machine  which  is  rilled  with  water  at  the  same  tem- 
perature. This  machine  consists  of  a  rectangular  water-tight 
box,  having  a  movable  block  working  on  a  worm  geaj  from 
left  to  right.  The  left  clip  is  held  rigid  by  placing  its  ring  over 
a  short  metal  peg  provided  for  this  purpose;  the  right  clip 
is  placed  over  a  similar  rigid  peg  .on  the  movable  block.  The 
movable  block  is  provided  with  a  pointer  which  moves  along 
a  centimeter  scale.  Before  starting  the  test,  the  centimeter 
scale  is  adjusted  to  the  pointer  at  zero.  Power  is  then  applied 
by  the  worm  gear  pulling  from  left  to  right  at  the  uniform  rate 
of  5  centimeters  per  minute.  The  distance,  in  centimeters, 
registered  by  the  pointer  on  the  scale  at  the  time  of  rupture 
of  the  thread  of  bitumen  is  taken  as  the  ductility  of  the 
material. 

Most   ductility  machines  are  equipped   for   testing   three 


64  VALUE    OF    DUCTILITY    TEST 

briquets  simultaneously.     The  test  is  almost  invariably  made 
at  25°  C.,  although  4°  C.  has  also  been  recommended. 

Value  of  Test 

As  ordinarily  applied,  the  ductility  test  is  of  little  value 
other  than  as  a  means  of  identification  when  considered  in  con- 
nection with  certain  other  tests  and  for  control  in  the  manu- 
facture of  certain  types  of  bituminous  materials,  especially 
when  the  blowing  process  is  used.  The  blowing  process  tends  to 
materially  reduce  the  ductility  of  an  asphalt  cement,  and  highly 
blown  products  almost  invariably  show  a  very  low  ductility 

For  a  given  penetration  at  25°  C.  those  materials  which  are 
most  susceptible  to  temperature  changes  are  the  most  ductile 
at  25°  C.  As  for  a  given  type  of  material  ductility  decreases 
with  penetration,  it  follows  that  most  materials  with  a  high 
ductility  at  25°  C.  show  a  very  low  ductility  at  4°  C.  Materials 
which  are  but  slightly  susceptible  to  temperature  changes,  such 
as  blown  asphalts,  as  a  rule  have  a  low  ductility  at  25°  C.,  but 
as  their  penetration  at  4°  C.  is  not  so  greatly  changed,  neither 
is  their  ductility.  If  the  ductility  test  is  considered  as  a  measure 
of  the  stretch  of  the  bituminous  material  when  incorporated 
in  a  pavement,  which  stretch  may  be  caused  by  contraction 
of  the  pavement,  it  would  appear  that  high  ductility  at  25°  C. 
should  in  many  cases  be  undesirable  because  it  represents  low 
ductility  at  the  low  temperatures  which  cause  material  con- 
traction. As  a  matter  of  fact,  it  is  more  than  doubtful  if  the 
test  as  conducted  in  any  way  represents  the  behavior  of  the 
comparatively  thin  films  of  material  as  they  exist  in  a  bitu- 
minous pavement.  The  theory  has  also  been  advanced  that 
ductility  is  a  measure  of  adhesiveness.  Certainly  those  mate- 
rials which  appear  to  be  most  sticky  at  normal  temperature 
show  a  high  ductility  at  normal  temperature,  but,  if  the  theory 
holds  true,  their  adhesiveness  falls  off  more  markedly  with 
decrease  in  temperature  than  does  the  initial  adhesiveness  of 
materials  with  a  normally  low  ductility.  Also,  if  this  theory 
is  unqualifiedly  admitted,  it  would  seem  reasonable  to  conclude 
that  the  adhesiveness  of  an  asphalt  cement  of,  say,  60  penetra- 


HEAT    TESTS 


65 


tion  is  less  than  that  of  the  same  type  of  asphalt  cement  of 
150  penetration.  The  binding  strength  of  the  former  is,  how- 
ever, known  to  be  higher.  From  the  above  it  is  evident  that 
correct  interpretation  of  the  ductility  test,  except  as  a  means 
of  identification  and  control,  is  no  simple  matter.  In  general, 
for  a  given  type  of  bituminous  material  the  ductility  decreases 
as  the  specific  gravity  increases. 


HEAT  TESTS 

FLASH  AND   BURNING  POINTS 

Open-Cup  Method 
Equipment: 

i  open-cup  oil  tester  with  Bunsen  burner.     (Fig.  17.) 
i  chemical  thermometer  o°  C.  to  400°  C. 
i  piece  of  6-millimeter  glass  tubing,  6  centimeters  in  length, 
one  end  of  which  has  been  drawn  to  a 
i -millimeter  opening.     Soft  rubber  tub- 
ing for  gas  connections. 
Method. — A  number  of  open-cup  oil  testers 
have  been  devised  which  are  similar  in  design 
and  give  practically  equivalent  results.     This 
type   is   shown   in   Fig.  17.     It   consists  of    a 
brass  oil  cup,  a,  of  about  100  cubic  centimeters 
capacity.    The  outer  vessel,  6,  serves  as  an  air 
jacket.    The  thermometer,  c}  is  suspended  from 
the  wire  support,  J,  directly  over  the  center  of 
the   cup   so   that   its  bulb  is  entirely  covered 
with  oil  but  does  not  touch  the  bottom  of  the 
cup.     A  testing  flame  is  obtained  from  a  jet 
of  gas  passed  through  a  piece  of  glass  tubing, 
and  should  be  about  5  millime- 
ters in  length. 

The  test  is  made  by  first  fill- 
ing the  oil  cup  with  the  material 
under  examination  to  within  FIG.  17.  Open-Cup  Oil  Tester 


66  CLOSED-CUP    METHOD 

about  5  millimeters  of  the  top.  The  Bunsen  flame  is  then 
applied  in  such  a  manner  that  the  temperature  of  the  ma- 
terial in  the  cup  is  raised  at  the  rate  of  5°  C.  per  minute. 
From  time  to  time  the  testing  flame  is  brought  almost  in 
contact  with  the  surface  of  the  oil.  A  distinct  flicker  or  flash 
over  the  entire  surface  of  the  oil  shows  that  the  flash  point  is 
reached  and  the  temperature  at  this  point  is  taken.  It  will 
usually  be  found  that  the  flash  point  as  determined  by  the 
open-cup  method  is  somewhat  higher  than  by  the  closed-cup 
method  for  the  same  material. 

The  burning  point  of  the  material  is  obtained  by  continu- 
ing the  test  and  noting  that  temperature  at  which  it  ignites 
and  burns.  The  flame  should  then  be  extinguished  by  means 
of  a  metal  cover  supplied  with  the  instrument.  No  attempt 
should  be  made  to  blow  out  the  flame,  for  fear  of  scattering 
the  burning  oil. 

Closed-Cup  Method 
Equipment: 

i  New  York  State  Board  of  Health  oil  tester  with  Bunsen 

burner.     (Fig.  18.) 

i  chemical  thermometer  reading  from  o°  C.  to  400°  C. 
i  piece  of  6-millimeter  glass  tubing,  6  centimeters  in  length, 
one  end  of  which  has  been  drawn  to  a  i-milHmeter  open- 
ing.    Soft  rubber  tubing  for  gas  connection, 
i  wire  frame  for  holding  thermometer. 

Method. — While  for  all  ordinary  purposes  the  open-cup 
method  of  determining  the  flash  and  burning  points  of  bitu- 
minous road  materials  is  satisfactory,  the  closed-cup  method 
is  to  be  preferred  where  greater  accuracy  is  required.  This  is 
particularly  true  for  materials  of  a  relatively  low  flash  point. 
The  New  York  State  Board  of  Health  oil  tester  is  ordinarily 
used  for  testing  materials  used  in  highway  engineering.  This 
tester,  shown  in  Fig.  18,  consists  of  a  copper  oil  cup,  a,  of  about 
300  cubic  centimeters  capacity,  which  is  heated  in  an  oil  bath, 
b,  by  a  small  Bunsen  flame.  The  cup  is  provided  with  a  glass 
cover,  c,  carrying  a  thermometer,  d,  and  a  hole,  e,  for  inserting 


CLOSED-CUP    METHOD 


67 


the  testing  flame.  The  testing  flame  is  obtained  from  a  jet  of 
gas  passed  through  the  piece  of  glass  tubing  and  should  be 
about  5  millimeters  in  length. 

The  flash  test  is  made  as  follows:  The  oil  cup  should  first 
be  removed  and  the  bath  filled  with  cottonseed  oil.  The  oil 
cup  should  be  replaced  and  rilled  with  the  material  to  be  tested 
to  within  3  m.il1i-m.et.ers  of  the  flange  joining  the  cup  and  the 
vapor  chamber  above.  The  glass  cover  is  then  placed  on  the 


FIG.  1 8.     New  York  State  Board  of  Health  Oil  Tester 

oil  cup  and  the  thermometer  so  adjusted  that  its  bulb  is  just 
covered  by  the  bituminous  material.  The  Bunsen  flame  should 
be  applied  in  such  a  manner  that  the  temperature  of  the  mate- 
rial in  the  cup  is  raised  at  the  rate  of  5°  C.  per  minute.  From 
time  to  time  the  testing  flame  is  inserted  in  the  opening  in 
the  cover  to  about  half  way  between  the  surface  of  the  material 
and  the  cover.  The  appearance  of  a  faint  bluish  flame  over  the 
entire  surface  of  the  bitumen  shows  that  the  flash  point  has 
been  reached  and  the  temperature  at  this  point  is  taken. 

The  burning  point  of  the  material  may  now  be  obtained  by 
removing  the  glass  cover  and  replacing  the  thermometer  in  a 
wire  frame.  The  temperature  is  raised  at  the  same  rate  and 
the  material  tested  as  before.  The  temperature  at  which  the 
material  ignites  and  burns  is  taken  as  the  burning  point. 


68     VALUE  OF  FLASH-  AND  BURNING-POINT  DETERMINATIONS 

At  the  conclusion  of  this  test  the  flame  should  not  be  blown 
out,  for  danger  of  splashing  the  hot  material.  A  metal  cover 
or  extinguisher  should  be  employed  for  this  purpose  by  placing 
it  over  the  ignited  material. 

Value  of  Flash-  and  Burning-Point  Determinations 

The  flash  and  burning  point  determinations  are  of  value  as 
a  quick  means  of  differentiating  heavy  crude  and  fluid  residual 
products.  All  crude  fluid  bituminous  materials  have  much 
lower  flash  points  than  residuals,  the  flash  points  of  which  in- 
crease as  the  temperature  of  distillation  at  which  they  are  pro- 
duced increases.  In  general,  for  a  given  type  of  material,  the 
lower  its  specific  gravity  the  lower  its  flash  point.  Cut-back 
products  produced  with  a  light  volatile  flux  necessarily  show 
a  lower  flash  point  than  do  straight  residuals  of  the  same  vis- 
cosity, float  test,  or  penetration,  and  are  thus  quickly  indicated. 
The  flash  point  of  asphalt  cements  which  are  not  cut-back 
products  almost  invariably  exceeds  163°  C.  and  is  usually  higher 
than  200°  C.  Under  certain  working  conditions  the  tempera- 
ture at  which  a  material  flashes  may  be  considered  as  a  danger 
point,  and  in  specifications  the  flash-point  limit  is  often  placed 
at  a  higher  temperature  than  that  to  which  it  will  be  neces- 
sary to  heat  the  material  while  being  used.  Sometimes  the 
flash  and  burning  points  of  a  material  are  close  together  and 
in  other  cases  they  are  quite  far  apart.  The  relation  of  flash 
to  burning  point  is  largely  dependent  upon  the  amount  present 
in  the  material  of  that  volatile  constituent  which  first  flashes. 
The  flash  and  burning  points  of  a  mixture  of  hydrocarbons  are 
seldom  those  of  the  most  volatile  constituents,  as  the  presence 
of  the  heavier  bodies  tends  to  retard  volatilization  of  the  lighter. 
The  flash  and  burning  points  of  two  or  more  constituents  of  a 
mixture  are  not  additive,  so  that  those  of  the  mixture  cannot 
be  predetermined.  The  mixture  should,  however,  show  flash 
and  burning  points  lying  between  those  of  the  constituents. 
In  reporting  results  and  in  specifying,  the  type  of  cup  should 
be  indicated,  as  the  open  cup  usually  gives  considerably  higher 


VOLATILIZATION    TEST  69 

results  than  the  closed  cup,  in  which  the  evolved  vapors  are 
more  or  less  confined. 

VOLATILIZATION  TEST 

Old  Method 
Equipment: 

i  constant-temperature  hot-air  oven  with  rubber  tubing. 
(Fig.  19.) 

1  thermo-regulator.     (Fig.  190.) 

2  chemical  thermometers  reading  from  —  10°  C.  to  250°  C. 
2  tin  boxes,  6  centimeters  in  diameter  and  2  centimeters 

deep. 

i  analytical   balance,   capacity   100  grams,   sensitive   to 
o.i  milligram. 

Method. — The  object  of  the  volatilization  test  is  to  deter- 
mine the  percentage  of  loss  which  the  material  undergoes  when 
a  given  weight  of  the  material  in  a  standard-sized  container  is 
subjected  to  a  uniform  temperature  of  163°  C.  for  five  hours, 
and  also  to  ascertain  any  changes  in  the  character  of  the  mate- 
rial due  to  such  heating.  The  test  as  commonly  made  in  con- 
nection with  asphalts,  fluxes,  and  asphalt  cements,  called  for  a 
20-gram  sample  in  a  tin  box  6  centimeters  in  diameter  and  2 
centimeters  deep,  but  for  a  number  of  reasons  a  50-gram  sample 
in  a  box  3.5  centimeters  deep,  as  called  for  in  the  new  method, 
is  to  be  preferred. 

The  oven  shown  in  Fig.  19,  known  as  the  New  York  Testing 
Laboratory  oven,  is  most  commonly  used,  although  any  other 
form  may  be  used  that  will  give  a  uniform  temperature  through- 
out all  parts  where  samples  are  placed.  The  oven  is  cylindrical 
in  shape  and  consists  of  an  inner  compartment  fitted  with  a 
circular,  perforated  metal  shelf  for  holding  the  samples  under 
test.  This  shelf  should  be  covered  with  a  heavy  perforated 
sheet  of  asbestos  to  minimize  the  direct  conduction  of  heat 
from  the  metal  to  the  sample  holders.  A  cylindrical  outer 
compartment,  equipped  with  a  hinged  cover  at  the  top,  is  fitted 
over  the  inner  compartment,  leaving  an  air  space  between  the 


70 


VOLATILIZATION    TEST 


two.  The  oven  is  heated  from  below  by  means  of  a  ring  burner 
with  perforations  systematically  placed  so  as  to  equalize  the 
flames  as  nearly  as  possible.  The  top  or  cover  of  the  oven 
contains  a  number  of  openings  to  allow  air  circulation  or  the 
insertion  of  thermometers  and  gas  regulator.  The  oven  is  usu- 
ally equipped  with  a  fan  or  air  stirrer  below  the  shelf  which 
may  be  operated  from  a  pulley  connected  to  a  shaft  which  ex- 
tends upward  through  the  center  opening  in  the  top.  Use  of 
the  fan  during  the  test  has,  however,  been  generally  discon- 
tinued. A  gas  regulator  is  inserted  through  one  of  the  open- 


FiG.  19.     New  York  Testing  Laboratory  Oven 

ings  in  the  top  of  the  oven,  and  two  thermometers  are  inserted 
through  others.  The  bulb  of  one  of  the  thermometers  is  im- 
mersed in  a  sample  of  some  fluid,  non-volatile  bitumen,  while 
the  other  is  kept  in  air  at  the  same  level.  The  first  thermometer 
serves  to  show  the  temperature  of  the  samples  during  the  test, 
while  the  latter  gives  prompt  warning  of  any  sudden  changes 
in  temperature  due  to  irregularities  in  the  gas  pressure,  etc. 

Before  making  the  test  the  interior  of  the  oven  should  show 
a  temperature  of  163°  C.  as  registered  by  the  thermometer  in 
air.  The  tin  box  is  accurately  weighed  after  carefully  wiping 
with  a  towel  to  remove  any  grease  or  dirt.  About  20  grams 
of  the  material  to  be  tested  are  then  placed  in  the  box.  The 


NEW    METHOD  71 

material  may  first  be  weighed  on  a  rough  balance,  if  one  is 
at  hand,  after  which  the  accurate  weight,  which  should  not 
vary  more  than  0.2  gram  from  the  specified  amount,  is  obtained. 
It  may  be  necessary  to  warm  some  of  the  material  in  order  to 
handle  it  conveniently,  after  which  it  must  be  allowed  to  cool 
before  determining  the  accurate  weight. 

The  sample  should  now  be  placed  in  the  oven,  where  it  is 
allowed  to  remain  for  a  period  of  five  hours,  during  which  time 
the  temperature  as  shown  by  the  thermometer  in  bitumen 
should  not  vary  at  any  time  more  than  2°  C.  from  163°  C.  The 
sample  is  then  removed  from  the  oven,  allowed  to  cool,  and 
reweighed.  From  the  olifference  between  this  weight  and  the 
total  weight  before  heating,  the  percentage  of  loss  on  the  amount 
of  material  taken  is  calculated. 


New  Method 

Equipment: 

i  constant-temperature  oven  with  revolving  shelf.  (Fig. 
20.) 

1  chemical  thermometer  reading  to  250°  C. 

2  tin  boxes,  5.5  centimeters  in  diameter  by  3.5  centimeters 
deep. 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 
milligram. 

Method.— This  method  is  substantially  the  "Standard  Test 
for  Loss  on  Heating  of  Oil  and  Asphaltic  Compounds"  recom- 
mended to  the  American  Society  tor  Testing  Materials  in  1916 
by  its  committee  D-4.  The  following  description  is,  however, 
limited  to  a  single  type  of  apparatus  and  the  directions  are 
more  specific  than  those  given  in  the  method  mentioned. 

A  Frease  electric  oven  with  thermo-regulator  and  equipped 
with  a  motor  and  revolving  shelf,  as  shown  in  Fig.  20,  will  be 
found  convenient  for  this  test.  The  door  of  the  oven  is  pro- 
vided with  a  glass  window  for  observing  the  thermometer,  which 
is  entirely  enclosed.  The  revolving  shelf  (see  Fig.  21)  was 
devised  by  Fitch  as  a  means  of  equalizing  the  temperature  of 


72  NEW    METHOD 

a  number  of  samples  tested  at  the  same  time  without  reference 
to  variations  in  temperature  at  various  positions  in  the  oven. 
A  circular  tin  box,  approximately  5.5  centimeters  in  diameter 
and  3.5  centimeters  deep,  is  first  accurately  weighed.  The  Amer- 
ican Can  Company's  Gill  style  ointment  box,  deep  pattern,  is 
most  commonly  used  for  this  purpose.  About  50  grams  of  the 


FlG.  20.     Frease  Electric  Oven  with  Revolving  Shelf 

material  under  examination  are  then  accurately  weighed  into  the 
box,  and  this  weight  should  not  vary  more  than  0.2  gram  from 
the  specified  amount.  The  box  and  sample  are  then  placed  in 
the  oven,  which  is  first  brought  to  the  prescribed  temperature, 
usually  163°  C.,  and  maintained  to  within  i  degree  of  that  tem- 
perature throughout  the  test.  The  temperature  reading  is  ob- 
tained from  a  thermometer  whose  bulb  is  immersed  in  a  dummy 
sample  of  the  material  resting  in  the  same  relative  position  as 


CONDITIONS    AFFECTING    THE    VOLATILIZATION    TEST        73 

the  original  sample  in  a  tin  box  on  the  shelf.  When  a  number 
of  samples  are  tested  at  the  same  time  they  are  placed  in  a 
single  row  upon  the  shelf.  The  shelf  itself  is  circular  in  shape 
and  perforated.  It  is  suspended  by  a  vertical  shaft  midway 
in  the  oven  and  is  revolved  by  means  of  the  motor  at  the  rate 
of  from  five  to  six  revolutions  per  minute. 

The  material  is  heated  for  a  period  of  5  hours,  after  which 
it  is  cooled  to  room  temperature  and  again  weighed  to  deter- 
mine the  per  cent  of  loss  which  it  has  suffered  during  the  test. 


SECTION.  A-B 


9  Holes  and 
Spaced  Equally 


TOP  VIEW 

FIG.  21.     Details  of  Revolving  Shelf 

When  additional  periods  of  heating  are  required  they  should 
be  made  in  successive  increments  of  5  hours  each.  If  the  residue 
after  heating  is  to  be  tested  for  consistency  it  should  be  melted 
and  thoroughly  mixed  by  stirring  until  cool. 

Conditions  Affecting  the  Volatilization  Test 

Besides  the  oven  itself  and  the  temperature  employed,  there 
are  a  number  of  other  conditions  that  affect  the  volatilization 
test.  The  most  important  of  these  is  the  relation  of  exposed 
surface  area  to  the  volume  of  sample  tested.  This  means  that 
for  a  given  diameter  of  container  variable  percentages  of  loss 


74  VALUE    OF    THE    VOLATILIZATION    TEST 

by  volatilization  will  occur  for  different  volumes  or  weights 
of  a  given  sample  which  is  tested.  This  is  particularly  true 
for  materials  that  show  a  high  loss  under  the  test,  and  as  the 
consistency  of  the  residue  is  largely  dependent  upon  the  per- 
centage of  loss  by  volatilization,  it  follows  that  for  a  given 
temperature  and  time  of  test  the  consistency  of  the  residue  will 
vary  with  the  relation  of  the  diameter  of  the  container  and 
the  weight  of  sample  tested.  It  will  be  noted  that  in  the  two 
methods  above  described  the  diameter  specified  for  the  con- 
tainer is  approximately  the  same,  but  that  one  method  specifies 
a  2o-gram  sample  while  the  other  specifies  a  5o-gram  sample. 
In  reporting  results,  therefore,  it  is  customary  to  indicate  the 
weight  of  sample  tested  as  well  as  the  temperature  and  time 
of  test.  The  2o-gram  sample  has  been  most  commonly  used 
for  the  harder  grades  of  asphalt  cements,  but,  as  this  amount 
does  not  afford  sufficient  depth  for  a  determination  of  the  pene- 
tration of  the  residue  obtained  from  the  softer  asphalt  cements, 
a  strong  preference  is  being  shown  for  the  5o-gram  sample. 

Value  of  the  Volatilization  Test 

The  volatilization  test  at  163°  C.  is  commonly  made  upon 
petroleum  and  asphalt  products  but  seldom  upon  tar  products. 
The  temperature  was  originally  selected  as  being  that  at  which 
a  refined  asphalt  is  usually  fluxed  to  produce  an  asphalt  cement. 
With  few  exceptions  it  may  also  be  considered  as  the  maximum 
allowable  temperature  to  heat  bituminous  materials  for  direct 
use.  Materials  which  are  likely  to  be  heated  to  this  tempera- 
ture should  show  a  low  loss  under  the  volatilization  test  and 
the  residue  should  not  show  an  undue  amount  of  hardening 
as  compared  with  the  original  sample.  When  testing  fluid 
products,  such  as  carpeting  mediums,  the  residue  from  the 
volatilization  test  may  be  subjected  to  the  float  test  if  too 
soft  for  its  penetration  to  be  determined.  This  is  particularly 
advisable  where  the  float  test  can  be  made  upon  both  the  orig- 
inal material  and  its  residue.  In  some  cases  the  volatilization 
test  is  made  at  other  temperatures  than  163°  C.  Thus  the  ten- 


DEHYDRATION — DETERMINATION    OF    WATER  75 

dency  of  a  material  to  harden  very  rapidly  after  use  is  shown 
by  a  test  at  100°,  105°,  or  110°  C.  If  the  test  is  to  be  made 
upon  a  tar  product,  a  relatively  low  temperature  should  be 
used,  as  163°  C.  is  unnecessarily  severe  for  tars,  owing  to  the 
fact  that  it  is  never  necessary  to  heat  them  to  this  temperature 
during  use,  and  if  they  are  so  heated  they  are  apt  to  be  seriously 
injured.  In  general,  for  a  given  type  of  residual  product,  the 
loss  by  volatilization  decreases  with  increase  in  specific  gravity, 
flash  point,  and  specific  viscosity  or  float  test,  and  decrease  in 
penetration  if  it  is  a  semisolid  or  solid. 

DEHYDRATION — DETERMINATION  OF  WATER 

Equipment: 

i  800  cubic  centimeter  cylindrical  copper  still  with  ring 
burner  and  rubber  tubing. 

1  Bunsen  burner. 

2  iron  stands. 

2  small  iron  clamps. 

i  iron  ring  support. 

i  long  piece  of  glass  tubing,  bent  for  a  condenser. 

i  special  form  separatory  funnel  with  graduated  stem. 
Method. — When  it  is  desired  to  dehydrate  a  bituminous 
material  prior  to  making  other  tests  or  to  determine  the  per- 
centage of  water  which  it  contains,  a  cylindrical  copper  still 
with  ring  burner,  as  shown  in  Fig.  22,  will  prove  convenient. 
From  250  to  500  cubic  centimeters  of  the  material  are  accurately 
weighed  into  the  still  and  a  thin  paper  gasket  tightly  clamped 
between  the  still  and  still  head.  The  apparatus  is  then  set 
up  as  shown  in  Fig.  22.  A  low  flame  is  then  applied  to  the 
upper  part  of  the  retort  and  the  heating  slowly  and  carefully 
continued  until  the  volume  of  water  in  the  special  graduated 
form  of  separatory  funnel  shows  no  further  increase.  The  vol- 
ume of  water  collected,  which  settles  to  the  bottom  of  the  funnel, 
is  noted  and  calculated  upon  a  percentage  basis  of  the  original 
sa'mple.  The  water  is  then  drained  from  the  separatory  funnel 
and  the  supernatent  layer  of  oil  is  run  into  and  thoroughly 


76 


DISTILLATION    TEST 


mixed  with  the  contents  of  the  still,  which  should  first  be  cooled 
to  below  100°  C. 

Value  of  Test 

Because  of  the  tendency  of  bituminous  materials  containing 
only  a  small  amount  of  water  to  foam  when  heated,  the  dehy- 
dration test  is  of  particular  value  in  preparing  materials  for 


FlG.  22.     Dehydrating  Apparatus 

any  of  the  consistency  and  heat  tests.  It  is  also  of  service  in 
actually  determining  the  amount  of  water  present  which  may 
have  a  marked  effect  upon  both  the  chemical  and  physical  prop- 
erties of  the  material.  When  making  a  determination  of  water 
in  semisolid  and  solid  products,  it  is  sometimes  advisable  to 
first  render  the  sample  fluid  by  the  addition  of  benzol  before 
attempting  the  distillation. 


DISTILLATION  TEST 

Flask  Method 
Equipment: 

i  250  cubic  centimeter  Engler  distillation  flask, 
i  chemical  thermometer  reading  from  —  5°  C.  to  400°  C. 
i  special  form  condenser  with  rubber  tubing. 
6  25  cubic  centimeter  glass  cylinders  graduated  to  o.i  cubic 
centimeter. 


FLASK    METHOD  77 

i  iron  stand. 

1  iron  ring  support  9  centimeters  in  diameter. 

2  cork-lined  universal  clamps. 

i  tin  shield,  20  centimeters  long  and  9  centimeters  in 

diameter, 
i  pinch  cock. 

i  Bunsen  burner  with  rubber  tubing, 
i  rough  balance,  capacity  i  kilogram,  sensitive  to  o.i  gram, 
i   analytical  balance,   capacity 
100   grams,  sensitive   to  o.i 
milligram. 

Method. — This  method  has  been 
recently  recommended  to  The  Ameri- 
can Society  for  Testing  Materials 
by  its  Committee  D~4  for  adoption 
as  standard.  The  exact  wording  of 
the  proposed  standard  method  has 
not  here  been  followed,  however,  as 
it  has  been  thought  advisable  to  FlG>  23>  Engler  Distilling 
include  a  few  additional  details  for  Flask 

the  use  of  beginners. 

The  Engler  flask,  shown  in  Fig.  23,  should  meet  the  follow- 
ing requirements  within  an  allowance  of  3  per  cent  variation: 

Diameter  of  bulb 8.0  cm. 

Length  of  neck 15.0  cm. 

Diameter  of  neck 1.7  cm. 

Length  of  tubulature li.o  cm. 

Diameter  of  tubulature 0.9  cm. 

Angle  of  tubulature 75° 

The  thermometer  should  be  made  of  resistance  glass  such 
as  Jena  59,  Jena  19,  or  Verra  dur.  It  should  be  filled  with 
carbon  dioxide  under  pressure  of  one  atmosphere  at  300°  C.  and 
should  be  provided  with  an  expansion  bulb  at  the  top.  It 
should  be  annealed  at  400°  C.  for  96  hours  and  slowly  cooled. 
It  should  be  graduated  in  single  degrees  Centigrade  from  —  5°  C. 
to  400°  C.,  the  length  of  the  graduations  from  o°  to  400°  C.  being 
from  29  to  31  centimeters  and  the  diameter  of  the  stem  from 
6  to  8  millimeters.  Starting  at  a  temperature  of  26°  C.  the 


78 


FLASK    METHOD 


mercury  should  pass  the  90°  mark  in  not  less  than  6  seconds 
when  plunged  into  a  free  flow  of  steam. 

Before  use  in  the  distillation  test  on  bituminous  materials, 
the  thermometer  should  be  calibrated  by  setting  up  the  entire 
apparatus,  as  shown  in  Fig.  24,  and  noting  the  apparent  tem- 
peratures at  which  three  chemically  pure  substances  of  known 
boiling  point  distill.  One  hundred  cubic  centimeters  of  distilled 

water,  chemically  pure  naphthalene 
and  chemically  pure  benzophenone  are 
used  for  this  purpose.  Their  normal 
boiling  points  are  100°,  218.2°,  and 
305°  C.  respectively.  The  boiling 
points  of  these  substances,  of  course, 
vary  with  the  barometric  pressure, 
but  if  the  thermometer  is  calibrated 
at  a  time  when  the  barometer  indi- 
cates about  the  average  pressure  for  a 
given  laboratory,  the  variations  in  re- 
sults due  to  varying  pressures  when  the 
thermometer  is  afterwards  used  for 
distillation  will  be  no  greater  than 
the  probable  errors  in  distillation. 
The  intermediate  readings  of  the 
thermometer  are  obtained  by  plotting 
the  results  as  shown  in  Fig.  25. 
Thus,  if  it  is  desired  to  make  a  cut  at 

170°  C.  during  a  distillation,  it  is  evident  that  the  cut  should 
be  made  under  with  this  particular  thermometer  at  an  ob- 
served temperature  of  167°.  The  correctness  of  the  thermome- 
ter should  be  checked  at  two  temperatures  after  each  third  dis- 
tillation until  the  thermometer  is  thoroughly  seasoned. 

The  condenser  used  in  connection  with  the  distilling  flask 
may  be  made  by  bending  a  standard  condenser  tube  as  shown 
in  Fig.  24  and  passing  it  through  a  tight-fitting  stopper  placed 
in  the  bottom  of  an  ordinary  Welsbach  lamp  chimney.  A  bent 
tube  carrying  a  short  length  of  rubber  tubing  and  a  pinch  cock 
is  also  fitted  into  the  stopper  for  the  purpose  of  draining  the 


FIG.  24.    Distillation  Appa- 
ratus—Flask Method 


FLASK    METHOD 


79 


condenser   of   cooling  water  if   desired.     The   condenser   tube 
when  straight  should  have  the  following  dimensions: 

Adapter 70  mm. 

Length  of  straight  tube 185  mm. 

Width  of  tube 12-15  mm. 

Width  of  adapter  end  of  tube 20—25  mm. 

If  the  material  to  be  tested  contains  water,  it  should  first 
be  dehydrated  or  otherwise  it  is  apt   to   foam  over   during 


mm 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

% 

uha 

le 

H 

/ 

i 
i 

i 

/ 

i 

/ 

/ 

i 

i 

— 

-/ 

i 
i 

/ 

V 

er 

i 
i 

/ 

/ 

/ 

I 

1 

/ 

i 

c 

10 

0 

•2(. 

0 

m 

Actual  Temperature 


FIG.  25.    Example  of  Thermometer  Calibration  Chart 

distillation.  The  specific  gravity  of  the  water-free  material  is 
determined  so  that  the  weight  of  100  cubic  centimeters  may  be 
calculated.  In  making  the  test  the  flask  should  first  be  sup- 
ported in  a  vertical  position  on  one  pan  of  the  rough  balance 
and  its  tare  accurately  obtained.  After  warming,  if  necessary, 
and  thoroughly  stirring  the  sample,  100  cubic  centimeters  are 
poured  into  the  tared  flask  and  weighed.  A  cork  stopper  car- 
rying the  thermometer  is  then  inserted  in  the  neck  of  the  flask 
so  that  the  top  of  the  bulb  is  opposite  the  middle  of  the  tubula- 
ture.  The  entire  apparatus  is  then  set  up  as  shown  in  Fig.  24. 
A  tin  shield  with  small  sight  hole  for  observing  the  Bunsen 
flame  surrounds  the  flask  and  burner  in  order  to  obviate  the 
influence  of  drafts.  The  glass  graduates  which  have  previously 


80  RETORT    METHOD 

been  weighed  to  within  o.i  gram  are  used  as  receivers 
for  the  distillate  fractions.  In  preparing  for  the  test  it  will 
be  found  convenient  to  mark  permanently  on  the  foot  of  each 
graduate  its  weight. 

The  material  should  be  heated  gradually  by  means  of  the 
Bunsen  burner,  and  the  heat  should  be  so  regulated  as  to  main- 
'tain  distillation  at  the  constant  rate  of  i  cubic  centimeter  per 
minute.  When  the  thermometer  just  passes  a  temperature  cor- 
responding to  no°C.,  the  graduated  cylinder  containing  the 
first  fraction  is  replaced  by  another.  The  receiver  is  changed 
again  at  170°  C.,  235°  C.,  and  at  270°  C.,  using  as  many  gradu- 
ated cylinders  as  may  be  necessary  without  allowing  any  to 
become  filled  above  the  25  cubic  centimeter  mark.  When  solid 
matter  deposits  upon  the  sides  of  the  condenser,  it  may  be 
melted  by  pouring  hot  water  through  the  condenser,  and  col- 
lected in  the  fraction  to  which  it  belongs.  The  last  fraction 
is  collected  up  to  300°  C.,  after  which  the  flask  and  graduates 
are  cooled  to  room  temperature,  and  their  contents  determined 
by  volume  and  weight.  The  volume  of  pitch  remaining  in  the 
retort  is  found  by  deducting  the  total  volume  of  the  distillates 
from  the  original  100  cubic  centimeters  taken.  Note  should  be 
made  of  the  approximate  volume  of  solids  which  precipitate 
from  the  distillates  upon  cooling  to  25°  C. 

The  results  obtained  are  calculated  in  percentages  by  vol- 
umes and  weights  to  tenths  of  i  per  cent  and  reported  as  follows : 


Distillate 

Per  cent 
by  volume 

Per  cent 
by  weight 

I    ^fater  or  arnrnoniacal  liquor 

2.  First  light  oils  to  110°  C  
3.  Second  light  oils  110°  C.  to  170°  C.  .  . 
4    Heavy  oils  170°  C.  to  270°  C  . 



5    Heavy  oils  270°  C.  to  300°  C  

6    Pitch  residue 

Retort  Method 
Equipment: 

i  8  oz.  stoppered  glass  retort. 

i  chemical  thermometer  reading  from  —5°  C.  to  400°  C. 


RETORT    METHOD 


81 


1  condensing  tube. 

625  cubic  centimeter  glass  cylinders  or  bottles. 

2  iron  stands. 

2  cork-lined  universal  clamps. 

i  iron  ring  support. 

i  tin  shield. 

i  Bunsen  burner  with  rubber  tubing. 

i  rough  balance,  capacity  i  kilogram,  sensitive  to  o.i  gram. 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 

milligram. 

Method. — While  the  flask  method  is  well  adapted  to  the  dis- 
tillation of  all  water-free  bituminous  materials  and  has  been 
more  accurately  standardized,  the  following  method  has  been 


^-Thermometer 


FIG.  26.     Distillation  Apparatus. — Retort  Method 

and  is  now  widely  used  in  the  distillation  of  creosoting  oils. 
It  is  known  as  the  Standard  Creosoters'  Method.  The  following 
description  is  essentially  the  same  as  published  in  Bulletin  65 
of  the  American  Engineering,  Railway,  and  Maintenance  of 
Way  Association,  although  the  wording  is  different  to  some 


82  RETORT    METHOD 

extent,  and  certain  details  have  been  added  in  accordance  with 
the  tentative  method  recommended  in  1915  by  Committee  D-; 
of  the  American  Society  for  Testing  Materials. 

The  retort,  as  shown  in  Fig.  26,  should  have  a  capacity  of 
eight  ounces  up  to  the  bend  of  the  neck  when  the  bottom 
of  the  retort  and  the  mouth  of  the  offtake  are  in  the  same 
horizontal  plane.  The  thermometer  should  be  nitrogen-filled 
and  divided  into  full  degrees  Centigrade.  It  should  have  the 
following  dimensions: 

Total  length,  375  mm.;  tolerance,  10  mm. 
Bulb  length,  14  mm. ;  tolerance,  i  mm. 
Distance  from  zero  mark  to  bottom  of  bulb,  30  mm. ;  tol- 
erance, 4  mm. 

Scale  length  from  zero  mark  to  400°  C.,  295  mm.;   toler- 
ance, 5  mm. 

Diameter  of  stem,  7  mm.;  tolerance,  i  mm. 
Diameter  of  bulb,  6  mm. ;  tolerance,  i  mm. 
The  bulb  of  the  retort  and  at  least  two  inches  of  the  neck 
should  be  covered  with  a  shield  of  heavy  asbestos  paper  shaped 
as  shown  in  Fig.  27.     When  making  the  dis- 
tillation, two  sheets  of  2o-mesh  wire  gauze, 
six  inches  square,  are  inserted  between  the 
bottom  of  the  retort  and  the  flame  of  the 
burner.     The  flame  is  protected  against  air 
currents  by  means  of  a  tin  shield  attached 
to  the  burner. 

Before  beginning  the  distillation  the  re- 
tort should  be  carefully  weighed.  The  oil 
should  be  well  mixed  and  if  solids  are  pres- 

FIG.  27.     Asbestos  .  r, 

Shield  for  Retort  en^  should  be  entirely  liquefied  by  heating. 
If  it  contains  water  it  should  be  dehydrated 
prior  to  the  test.  Exactly  100  grams  of  the  water-free  oil 
should  then  be  weighed  into  the  retort.  The  thermometer 
should  next  be  inserted  through  a  tight-fitting  cork  stopper 
in  the  tubulature  of  the  retort,  so  that  the  lower  end  of  the 
bulb  is  one-half  inch  from  the  surface  of  the  oil.  The  con- 
densing tube  is  then  attached  to  the  retort  by  a  tight  cork 


VALUE    OF    DISTILLATION    TEST  83 

joint  and  the  entire  apparatus  set  up  as  shown  in  Fig.  26. 
The  distance  between  the  bulb  and  the  end  of  the  condens- 
ing tube  should  be  not  less  than  20  nor  more  than  24  inches. 

Distillation  should  be  conducted  at  the  rate  of  from  i  to  2 
drops  per  second  and  the  distillate  collected  in  weighed  receivers. 
The  condenser  tube  should  be  warmed  when  necessary  to  pre- 
vent accumulation  of  solid  distillates.  The  receivers  should  be 
changed  as  the  mercury  passes  the  fractionating  point.  Frac- 
tions are  collected  and  weighed  as  follows: 


Up  to  170°  Centigrade 
From  170°  to  200°  Centigrade 

"    200°"  210° 

"  210°  «  235° 
270° 
3I5° 

315°  "  355° 


The  last  receiver  should  be  removed  at  355°  C.  without  drain- 
ing the  condenser.  The  various  fractions  should  be  reported 
upon  a  percentage  weight  basis.  In  reporting  results  under 
ordinary  conditions,  certain  of  the  fractions  are  taken  collec- 
tively and  the  total  number  of  fractions  reduced  as  follows: 


Up  to  200°  Centigrade 
200°  to  210°  Centigrade 


210°  "   235° 

235°  "   315° 
Above  315° 

Value  of  Distillation  Test 

The  distillation  test  as  applied  to  tars  is  valuable  both  as 
a  means  of  ascertaining  their  method  of  preparation  and  suit- 
ability for  a  given  purpose.  In  this  connection  it  takes  the 
place  of  the  volatilization  test  which  is  usually  restricted  to  the 
examination  of  petroleum  and  asphalt  products.  All  crude  tars 
contain  water,  and  the  appearance  of  water  in  the  distillate 


84  TOTAL    BITUMEN 

therefore  indicates  a  crude  material,  especially  if  accompanied 
by  an  appreciable  quantity  of  light  oil.  Heavy  refined  tars 
which  have  become  contaminated  with  water  show  a  sudden 
rise  in  distillation  temperature  after  the  water  has  been  removed. 
The  presence  of  high  percentages  of  naphthalene,  anthracene, 
etc.,  is  indicated  by  the  proportion  of  the  various  distillates 
which  solidify  upon  cooling.  In  this  connection  it  is  always 
well  to  note  the  character  of  each  fraction  obtained.  The  ex- 
tent of  distillation  in  the  manufacture  of  the  original  material 
is  indicated  by  the  temperature  at  which  distillation  commences 
in  the  test  and  the  relative  quantities  of  the  fractions  obtained. 
Cut-back  products  usually  show  an  abnormal  amount  of  some 
given  fraction  as  compared  to  the  amount  that  would  be  ob- 
tained from  a  straight  distilled  residue  of  the  same  consistency. 
After  the  distillation  test  is  completed  it  is  often  of  interest 
to  determine  the  melting  point  of  the  residue  which,  if  obtained 
by  distillation  by  the  flask  method  to  300°  C.,  should  seldom  ex- 
ceed 75°  C.  Various  fractions  are  also  frequently  examined  for 
the  purpose  of  identifying  the  material. 

In  general,  for  a  given  type  of  residual  material  the  percent- 
age of  total  distillate  to  any  given  temperature  decreases  as  the 
specific  gravity  and  viscosity  or  float  test  increase  and  as  the 
penetration  decreases. 


SOLUBILITY  TESTS   ON  OTHER  THAN 
BITUMINOUS  AGGREGATES 

TOTAL  BITUMEN 

Rapid  Method 
Equipment: 

i  100  cubic  centimeter  Erlenmeyer  flask. 

i  500  cubic  centimeter  flask  with  side  neck  for  filtering 

under  pressure, 
i  rubber  stopper  with  one  hole. 


RAPED    METHOD  85 

i  filter  tube,  3.9  centimeters  inside  diameter, 
i  platimun  or  porcelain  Gooch  crucible. 

1  piece  of  seamless  rubber  tubing,  about  3  centimeters  in 
diameter  and  3  centimeters  long. 

50  grams  of  long-fiber  amphibole  asbestos. 

2  wash  bottles:  i  for  solvent,  i  for  water, 
i  Bunsen  burner. 

i  nichrome  triangle. 

i  iron  tripod. 

i  drying  oven. 

i  desiccator  with  calcium  chloride. 

i  thermometer  reading  from  — 10°  C.  to  110°  C. 

i  vacuum  pump  and  connections. 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 

milligram. 

Method. — As  by  definition  all  bitumen  is  soluble  in  carbon 
disulphide,  the  per  cent  of  total  bitumen  in  a  bituminous  mate- 
rial is  ascertained  by  deterrnining  its  solubility  in  carbon  disul- 
phide. This  solvent  is  an  ethereal,  mobile  liquid  which  is  ex- 
tremely inflammable  and  should  therefore  be  handled  with  great 
care.  It  is  very  volatile  and  when  mixed  with  air  its  vapors 
spontaneously  ignite  at  a  temperature  slightly  higher  than  that 
of  live  steam.  It  should  therefore  never  be  used  in  the  vicinity 
of  a  free  flame  or  even  an  electric  hot  plate.  In  the  laboratory 
where  carbon  disulphide  is  used  it  is  always  advisable  to  have 
close  at  hand  a  chemical  fire  extinguisher  or  large  bottle  of  carbon 
tetrachloride,  which  in  itself  is  an  effective  fire  extinguisher. 

The  most  widely  used  method  of  making  the  total  bitumen 
determination  consists  in  dissolving  the  bitumen  in  carbon  disul- 
phide and  recovering  any  insoluble  matter  by  filtering  the  solu- 
tion through  an  asbestos  felt.  The  form  of  Gooch  crucible 
best  adapted  for  the  determination  is  4.4  centimeters  wide  at 
the  top,  tapering  to  3.6  centimeters  at  the  bottom,  and  is  2.5 
centimeters  deep. 

For  preparing  the  felt  the  necessary  apparatus  is  arranged 
as  shown  in  Fig.  28,  in  which  a  is  the  filtering  flask,  b  a  rubber 
stopper,  c  the  filter  tube,  and  d  a  section  of  rubber  tubing  which 


TOTAL    BITUMEN 


tightly  clasps  the  Gooch  crucible,  e.  The  asbestos  is  cut  with 
scissors  into  pieces  not  exceeding  i  centimeter  in  length,  after 
which  it  is  shaken  up  with  just  sufficient  water  to  pour  easily. 
The  crucible  is  filled  with  the  suspended  asbestos,  which  is  al- 
lowed to  settle  for  a  few  moments.  A  light  suction  is  then 
applied  to  draw  off  all  the  water  and  leave  a  firm  mat  of  as- 
bestos in  the  crucible.  More  of  the  suspended  material  is  added, 
and  the  operation  is  repeated  until  the  felt  is  so  dense  that  it 

scarcely  transmits  light  when  held 
so  that  the  bottom  of  the  crucible 
is  between  the  eye  and  the  source 
of  light.  The  felt  should  then  be 
washed  several  times  with  water, 
and  drawn  firmly  against  the  bot- 
tom of  the  crucible  by  an  increased 
suction.  The  crucible  is  removed 
to  a  drying  oven  for  a  few  minutes, 
after  which  it  is  ignited  at  red  heat 
over  a  Bunsen  burner,  cooled  in  a 
desiccator  and  weighed. 

From  i  to  2  grams  of  the  ma- 
terial under  examination  is  now 
placed  in  the  Erlenmeyer  flask, 
which  has  been  previously  weighed, 

and  the  accurate  weight  of  the  sample  is  obtained.  One 
hundred  cubic  centimeters  of  chemically  pure  carbon  disul- 
phide  are  poured  into  the  flask  in  small  portions,  with  continual 
agitation,  until  all  lumps  disappear  and  nothing  adheres  to  the 
bottom.  The  flask  is  then  corked  and  set  aside  for  15  minutes. 
After  being  weighed,  the  Gooch  crucible  containing  the  felt 
is  set  up  over  the  dry-pressure  flask,  as  shown  in  Fig.  28,  and 
the  solution  of  bitumen  in  carbon  disulphide  is  decanted  through 
the  felt  without  suction  by  gradually  tilting  the  flask,  with  care 
not  to  stir  up  any  precipitate  that  may  have  settled  out.  At 
the  first  sign  of  any  sediment  coming  out,  the  decantation  is 
stopped  and  the  filter  allowed  to  drain.  A  small  amount  of 
carbon  disulphide  is  then  washed  down  the  sides  of  the  flask, 


FIG.  28.     Apparatus  for  Total 
Bitumen  Determination 


RAPID    METHOD  87 

after  which  the  precipitate  is  brought  upon  the  felt  and  the 
flask  scrubbed,  if  necessary,  with  a  feather  or  "  policeman,"  to 
remove  all  adhering  material.  The  contents  of  the  crucible 
are  washed  with  carbon  disulphide  until  the  washings  run 
colorless.  Suction  is  then  applied  until  there  is  practically  no 
odor  of  carbon  disulphide  in  the  crucible,  after  which  the  out- 
side of  the  crucible  is  cleaned  with  a  cloth  moistened  with  a 
small  amount  of  the  solvent.  The  crucible  and  contents  are 
dried  in  the  hot-air  oven  at  100°  C.  for  about  20  minutes,  cooled 
in  a  desiccator,  and  weighed.  If  any  appreciable  amount  of 
insoluble  matter  adheres  to  the  flask,  it  should  also  be  dried 
and  weighed,  and  any  increase  over  the  original  weight  of  the 
flask  should  be  added  to  the  weight  of  insoluble  matter  in  the 
crucible.  The  total  weight  of  insoluble  material  may  include 
both  organic  and  mineral  matter.  The  former,  if  present,  is 
burned  off  by  ignition  at  a  red  heat  until  no  incandescent  par- 
ticles remain,  thus  leaving  the  mineral  matter  or  ash,  which 
can  be  weighed  by  cooling.  The  difference  between  the  total 
weight  of  material  insoluble  in  carbon  disulphide  and  the  weight 
of  substance  taken  equals  the  total  bitumen,  and  the  percent- 
age weights  are  calculated  and  reported  as  total  bitumen,  and 
organic  and  inorganic  matter  insoluble,  on  the  basis  of  the 
weight  of  material  taken  for  analysis. 
Results  are  usually  reported  as  follows: 

Total  Bitumen  (or  Material  Soluble  in  C^) 

Organic  Matter  Insoluble  (or  Free  Carbon  in  the  Case  of  Tars) 

Inorganic  Matter  Insoluble  (or  Ash) 


100.00% 

This  method  is  quite  satisfactory  for  straight  oil  and  tar 
products,  but  where  certain  natural  asphalts  are  present  it  will 
be  found  practically  impossible  to  retain  all  of  the  finely  divided 
mineral  matter  on  an  asbestos  felt.  It  is,  therefore,  generally 
more  accurate  to  obtain  the  result  for  total  mineral  matter 
by  direct  ignition  of  a  i-gram  sample  in  a  platinum  crucible 
or  to  use  the  result  for  ash  obtained  in  the  fixed  carbon  test. 
The  total  bitumen  is  then  determined  by  deducting  from  100 
per  cent  the  sum  of  the  percentages  of  total  mineral  matter  and 


88  LONG    METHOD 

organic  matter  insoluble.  If  the  presence  of  a  carbonate  min- 
eral is  suspected,  the  percentage  of  mineral  matter  may  be 
most  accurately  obtained  by  treating  the  ash  from  the  fixed 
carbon  determination  with  a  few  drops  of  ammonium  carbonate 
solution,  drying  at  100°  C.,  then  heating  for  a  few  minutes  at 
a  dull-red  heat,  cooling,  and  again  weighing. 

When  difficulty  in  filtering  is  experienced — for  instance, 
when  Trinidad  asphalt  is  present  in  any  amount — a  period  of 
longer  subsidence  than  15  minutes  is  necessary  and  the  follow- 
ing method  may  then  be  used: 

Long  Method 

Equipment. — Same  as  for  the  rapid  method  except  that  two  150  cubic 
centimeter  Erlenmeyer  flasks  are  required  in  place  of  one  100  cubic  centi- 
meter flask. 

Method. — The  following  method  was  adopted  in  191 1  by  The  American  Soci- 
ety for  Testing  Materials  and  is  particularly  adapted  for  use  in  connection  with 
products  such  as  Trindad  asphalt  which  contain  a  relatively  high  percentage 
of  very  finely  divided  mineral  matter  that  either  passes  through  or  tends  to 
clog  the  filtering  medium.  While  it  may  also  be  used  in  connection  with 
other  products,  it  will  in  some  cases  be  found  to  give  somewhat  lower  results 
in  the  percentage  of  total  bitumen,  owing  to  the  tendency  of  some  organic  mat- 
ter which  was  originally  soluble  to  precipitate  in  a  comparatively  dilute  solu- 
tion of  carbon  disulphide  upon  prolonged  standing.  The  Committee  in  pre- 
senting this  method  stated  that  they  wished  it  understood  that  they  do  not 
recommend  it  as  the  best  for  general  use,  as  it  is  longer  and  in  many  cases 
gives  no  better  results  than  other  more  expeditious  methods,  but  only  as  a 
method  to  be  resorted  to  in  case  of  dispute,  as  it  seems  to  have  the  widest 
range  of  applicability  of  any  of  the  methods  which  they  had  considered. 

"After  drying,  from  2  to  15  grams  (as  may  be  necessary  to  insure  the 
presence  of  I  to  2  grams  of  pure  bitumen)  are  weighed  into  a  I5o-c.c.  tared 
Erlenmeyer  flask  and  treated  with  100  c.c.  of  carbon  disulphide.  The  flask  is 
then  loosely  corked  and  shaken  from  time  to  time  until  all  large  particles  of  the 
material  have  been  broken  up.  It  is  then  set  aside  for  48  hours  to  settle.  The 
solution  is  decanted  into  a  similar  flask  that  has  been  previously  weighed.  As 
much  of  the  solvent  is  poured  off  as  possible  without  disturbing  the  residue. 
The  contents  of  the  first  flask  are  again  treated  with  fresh  carbon  disulphide, 
shaken  as  before,  and  then  put  away  with  the  second  flask  for  48  hours  to 
settle. 

"The  liquid  in  the  second  flask  is  then  carefully  decanted  upon  a  weighed 
Gooch  crucible,  3.2  cm.  in  diameter  at  the  bottom,  fitted  with  an  asbestos 
filter,  and  the  contents  of  the  first  flask  are  similarly  treated.  The  asbestos 
filter  is  made  of  ignited  long-fiber  amphibole,  packed  in  the  bottom  of  a  Gooch 
crucib'e  to  the  depth  of  not  over  yi  in.  In  filtering,  no  vacuum  is  to  be  used 
and  the  temperature  is  to  be  kept  between  20°  and  25°  C.  After  passing  the 
liquid  contents  of  both  flasks  through  the  filter,  the  residue  on  the  filter  is 
thoroughly  washed  and  the  residues  remaining  in  them  are  shaken  with  more 
fresh  carbon  disulphide  and  allowed  to  settle  for  24  hours,  or  until  it  is  seen 
that  a  good  subsidation  has  taken  place.  The  solvent  in  both  flasks  is  then 
again  decanted  through  the  filter  and  the  residues  remaining  in  them  are 
washed  until  the  washings  are  practically  colorless.  All  washings  are  to  be 
passed  through  the  Gooch  crucible. 


VALUE    OF    TOTAL    BITUMEN    DETERMINATION  89 

"The  crucible  and  both  flasks  are  then  dried  at  125°  C.  and  weighed.  The 
filtrate  containing  the  bitumen  is  evaporated,  the  bituminous  residue  burned, 
and  the  weight  of  the  ash  thus  obtained  added  to  that  of  the  residue  in  the 
two  flasks  and  the  crucible.  The  sum  of  these  weights  deducted  from  the 
weight  of  substance  taken  gives  the  weight  of  soluble  bitumen." 

Value  of  Total  Bitumen  Determination 

The  methods  above  described  are  best  suited  for  the  deter- 
mination of  total  bitumen  in  comparatively  pure  bituminous 
materials,  although  they  are  also  applicable  to  the  examination 
of  fine  bituminous  aggregates  when  it  is  not  desired  to  recover 
the  mineral  matter  for  the  purpose  of  grading  it  or  making  a 
mechanical  analysis.  As,  however,  it  is  usually  desired  to  grade 
the  aggregate,  one  of  the  methods  described  under  "Extraction 
of  Bituminous  Aggregates  and  Recovery  of  Bitumen"  is  usually 
to  be  preferred  for  such  products. 

As  bituminous  materials  are  sometimes  purchased  upon  their 
per  cent  of  total  bitumen,  the  determination  may  be  necessary 
as  a  basis  of  payment.  All  bituminous  distillates  produced  by 
fractional  distillation  are  completely  soluble  in  carbon  disul- 
phide. Residual  petroleum  products  should  also  be  almost 
completely  soluble.  A  small  amount  of  still  ash  and  extraneous 
organic  matter  is,  however,  usually  present,  and  an  allowance 
o'f  approximately  0.5  per  cent  may  therefore  be  made  for  total 
material  insoluble  in  carbon  disulphide.  If  the  organic  matter 
insoluble  exceeds  0.5  per  cent,  there  is  strong  indication  that 
the  petroleum  has  been  cracked  or  locally  overheated  with  pos- 
sible resultant  injury  to  the  finished  product.  Native  asphalts 
and  products  produced  by  fluxing  the  native  asphalts  ordinarily 
contain  appreciable  amounts  of  both  mineral  matter  and  or- 
ganic matter  insoluble  in  carbon  disulphide.  Gilsonite  is  one 
of  the  few  exceptions  to  the  rule.  Where  the  exact  percentage 
of  total  insoluble  matter  is  known  for  a  refined  native  asphalt, 
it  is  possible  to  compute  with  considerable  accuracy  the  amount 
of  such  asphalt  present  in  an  asphalt  cement  produced  by 
fluxing  it.  In  such  computation  the  petroleum  flux  is  assumed 
to  be  completely  soluble  unless  information  to  the  contrary 
has  been  secured.  Practically  all  of  the  material  in  tar  prod- 


90  ASPHALTENES 

» 

ucts  which  is  insoluble  in  carbon  disulphide  consists  of  organic 
matter  or  free  carbon,  and  the  percentage  of  free  carbon  is 
thus  determined.  Refined  water-gas  tars  may  be  distinguished 
from  refined  coal  tars  of  the  same  consistency  by  their  relatively 
small  percentage  of  free  carbon.  Gas-house  coal  tars,  particu- 
larly those  produced  from  horizontal  retorts,  may  usually  be 
distinguished  from  coke-oven  tars  and  vertical-retort  tars  by 
their  relatively  high  percentage  of  free  carbon.  For  refined  tars 
of  the  same  viscosity  or  float  test  the  specific  gravity  becomes 
higher  as  the  solubility  in  carbon  disulphide  decreases.  The 
same  is  true  of  asphalt  cements  produced  from  the  same  native 
asphalt  if  such  asphalt  contains  insoluble  material.  As  the 
solubility  of  a  bituminous  material  in  carbon  disulphide  is  en- 
tirely dependent  upon  the  non-bituminous  constituents  present, 
it  is  evident  that  no  definite  relations* can  be  expressed  between 
the  physical  and  chemical  properties  of  the  actual  bitumen 
present  and  the  solubility  of  the  material  in  this  solvent.  In 
other  words,  irrespective  of  specific  gravity,  consistency  and 
other  properties,  all  pure  bitumen  is  dissolved  by  carbon  disul- 
phide. An  oily,  greasy  distillate  is  therefore  just  as  much 
bitumen  as  a  hard,  brittle  residue. 

ASPHALTENES    OR    BITUMEN   INSOLUBLE    IN    PARAFFIN   NAPHTHA 

Equipment. — Same  as  for  the  total  bitumen  determination, 
rapid  method. 

Method. — This  determination  is  made  in  the  same  general 
manner  as  the  rapid  method  for  total  bitumen,  except  that 
100  cubic  centimeters  of  86°  to  88°  B.  paraffin  naphtha,  at  least 
85  per  cent  by  volume  distilling  between  35°  C.  and  65°  C.,  is 
employed  as  a  solvent  instead  of  carbon  disulphide. 

Petroleum  naphthas  are  not  definite  chemical  compounds, 
but  are  composed  of  a  number  of  hydrocarbons  which  vary 
in  character  and  quantity  according  to  the  petroleum  from 
which  they  have  been  distilled.  Their  solvent  action  upon 
petroleum  and  asphalt  products  therefore  varies  greatly.  Thus 
naphthas  produced  from  asphaltic  petroleums,  consisting  mainly 


ASPHALTENES  91 

of  naphthene  and  polymethylene  hydrocarbons,  are  much  more 
powerful  solvents  of  the  heavier  asphaltic  hydrocarbons  than  are 
the  paraffin  naphthas.  Moreover,  the  solvent  power  of  any  given 
type  of  naphtha  increases  with  its  specific  gravity.  As  the  main 
object  of  the  naphtha  insoluble  bitumen  test  is  to  separate  the 
heavier  hydrocarbons  of  an  asphaltic  nature  from  the  other 
constituents,  a  light  paraffin  distillate  is  usually  employed.  One 
of  86°  B.  gravity,  distilling  between  40°  and  65°  C.,  has  been 
used  to  a  considerable  extent,  as  is  also  an  88°  B.  naphtha,  the 
solvent  power  of  which  is  approximately  the  same  as  that  of 
the  86°  B.  products.  "Heavier  naphthas,  such  as  66°  B.  and 
72°  B.,  are  also  less  frequently  used. 

As  the  percentage  of  asphaltenes  as  determined  by  test  is 
largely  dependent  upon  the  gravity  and  type  of  naphtha  used 
as  a  solvent,  a  report  of  results  should  state  the  gravity  of  the 
naphtha  and  preferably  its  boiling-point  limits  as  well.  The 
determination  is  not  entirely  satisfactory,  and  investigations  have 
been  conducted  with  a  view  to  finding  some  solvent  of  definite 
chemical  composition  which  will  satisfactorily  replace  naphtha 
and  more  nearly  insure  uniform  results  on  the  part  of  different 
analysts.  Ethyl  alcohol  and  ether  have  been  suggested  for 
this  purpose,  but  have  not  been  generally  used. 

Considerable  difficulty  is  sometimes  experienced  in  breaking 
up  some  of  the  heavy  semisolid  bitumens;  the  surface  of  the 
material  is  attacked,  but  it  is  necessary  to  remove  some  of  the 
insoluble  matter  in  order  to  expose  fresh  material  to  the  action 
of  the  solvent.  It  is  therefore  advisable  to  heat  the  sample 
after  it  is  weighed,  allowing  it  to  cool  in  a  thin  layer  around 
the  lower  part  of  the  flask.  If  difficulty  is  still  experienced  in 
dissolving  the  material,  a  rounded  glass  rod  will  be  found  con- 
venient for  breaking  up  the  undissolved  particles.  Not  more 
than  one-half  of  the  total  amount  of  naphtha  required  should 
be  used  until  the  sample  is  entirely  broken  up.  The  balance 
of  the  100  cubic  centimeters  is  then  added,  and  the  flask  is 
twirled  a  moment  in  order  to  mix  the  contents  thoroughly, 
after  which  it  is  corked  and  set  aside  for  30  minutes. 

In  making  the  filtration  the  utmost  care  should  be  exercised 


92         VALUE    OF    THE    DETERMINATION    OF    ASPHALTENES 

to  avoid  stirring  up  any  of  the  precipitate,  in  order  that  the 
filter  may  not  be  clogged  and  that  the  first  decantation  may 
be  as  complete  as  possible.  The  sides  of  the  flask  should  then 
be  quickly  washed  down  with  naphtha  and,  when  the  crucible 
has  drained,  the  bulk  of  insoluble  matter  is  brought  upon  the 
felt.  Suction  may  be  applied  when  the  filtration  by  gravity 
almost  ceases,  but  should  be  used  sparingly,  as  it  tends  to  clog 
the  filter  by  packing  the  precipitate  too  tightly.  The  material 
on  the  felt  should  never  be  allowed  to  run  entirely  dry  until 
the  washing  is  completed,  as  shown  by  the  colorless  filtrate. 
When  considerable  insoluble  matter  adheres  to  the  flask  no 
attempt  should  be  made  to  remove  it  completely.  In  such  cases 
the  adhering  material  is  merely  washed  until  free  from  soluble 
matter,  and  the  flask  is  dried  with  the  crucible  at  100°  C.  for 
about  one  hour,  after  which  it  is  cooled  and  weighed.  The 
percentage  of  bitumen  insoluble  is  reported  upon  the  basis  of 
total  bitumen  taken  as  100. 

The  difference  between  the  material  insoluble  in  carbon 
disulphide  and  in  the  naphtha  is  the  bitumen  insoluble  in  the 
latter.  Thus,  if  in  a  certain  instance  it  is  found  that  the  mate- 
rial insoluble  in  carbon  disulphide  amounts  to  i  per  cent  and 
that  10.9  per  cent  is  insoluble  in  naphtha,  'the  percentage  of 
bitumen  insoluble  would  be  calculated  as  follows: 

Bitumen  insoluble  in  naphtha       10.9  — 


Total  bitumen  100  —  i 


Value  of  the  Determination 


=  10  per  cent. 


While  the  class  of  bodies  known  as  asphaltenes  in  petroleum 
and  asphalt  products  are  of  variable  nature,  it  may  be  said  that 
in  general  they  tend  to  give  body  and  consistency  as  well  as 
cementitiousness  to  the  materials  in  which  they  occur.  Thus 
the  native  asphalts  carry  a  high  percentage  of  asphaltenes  while 
the  fluid  native  bitumens  or  petroleums  carry  a  relatively  low 
percentage.  Paraffin  petroleums  contain  less  than  asphaltic 
petroleums,  and  petroleum  distillates,  which  possess  no  cemen- 
titiousness, contain  none  at  all.  Upon  distillation  of  a  petro- 


CARBENES  93 

leum  the  asphaltenes  tend  to  concentrate  in  the  residuum  and 
under  certain  conditions  new  asphaltenes  are  actually  formed. 
The  blowing  process,  by  causing  what  is  known  as  nucleus  con- 
densation of  certain  of  the  lighter  hydrocarbons,  forms  asphal- 
tenes, which  are  directly  responsible  for  the  gradual  change  of 
the  fluid  to  a  semisolid  or  solid.  Irrespective  of  their  method 
of  manufacture,  asphalt  cements  of  a  given  penetration  at  25°  C. 
usually  carry  asphaltenes  within  comparatively  narrow  percent- 
age limits  and,  at  least  for  a  given  type  of  asphalt  cement,  the 
penetration  is  found  to  decrease  as  the  percentage  of  asphaltenes 
increases.  The  percentage  of  asphaltenes  is  usually  additive 
and,  for  mixtures,  may  be  calculated  with  reasonable  accuracy 
from  the  amounts  present  in  the  individual  constituents  of  the 
mixture.  In  fluxing  a  hard  asphalt  to  any  higher  penetration, 
the  amount  of  flux  that  will  be  required  will,  therefore,  depend 
to  a  considerable  extent  upon  the  percentage  of  asphaltenes 
present  in  the  flux.  The  higher  this  percentage  the  more  will 
be  required.  Owing  to  the  unavoidable  variations  to  which  this 
determination  is  subject,  specification  limitations  of  the  per  cent 
of  bitumen  insoluble  in  naphtha  are  necessarily  wider  than 
though  a  definite  chemical  compound  was  the  solvent  used. 
The  determination  is  useful  as  a  means  of  identification  in  some 
instances,  particularly  when  considered  in  connection  with  other 
tests.  Of  the  solid  native  bituminous  materials,  Gilsonite  shows 
a  high  percentage  of  asphaltenes,  usually  over  45  per  cent,  while 
the  bitumen  of  grahamite  appears  to  be  almost  entirely  com- 
posed of  asphaltenes.  While  the  test  is  not  generally  applied 
to  tars,  it  is  of  interest  to  note  that  the  heavy  refined  tars  are 
almost  entirely  insoluble  in  light  paraffin  naphthas. 

CARBENES    OR   BITUMEN   INSOLUBLE   IN   CARBON   TETRACHLORIDE 

Equipment. — Same  as  for  the  total  bitumen  determination, 
rapid  method. 

Method. — This  determination  is  made  in  exactly  the  same 
manner  as  the  total  bitumen  determination,  except  that  chem- 
ically pure  carbon  tetrachloride  is  used  as  a  solvent  in  place 
of  carbon  disulphide. 


94  VALUE    OF    THE    DETERMINATION    OF    CARBENES 

Carbon  tetrachloride  is  a  volatile,  non-inflammable  liquid, 
which  is  almost  as  powerful  a  solvent  for  bitumen  as  carbon 
disulphide.  It  is  widely  used  as  a  fire  extinguisher,  and  it  is 
advisable  to  keep  a  bottle  of  the  material  in  the  laboratory 
for  that  purpose.  It  is  a  definite  chemical  compound  having 
the  formula  CC14.  In  the  presence  of  some  organic  matter, 
especially  in  direct  sunlight,  it  tends  to  decompose  slowly  and 
liberate  hydrochloric  acid,  although  under  ordinary  conditions 
it  is  chemically  stable.  With  the  bitumen  which  it  first  dis- 
solves it  may  later  react  to  precipitate  a  small  amount  of  in- 
soluble material.  This  property  must  be  taken  into  account 
in  its  use  as  a  solvent  and  a  short  period  of  digestion  is  there- 
fore adopted  in  order  to  prevent  a  determination  of  more  insoluble 
material  than  is  really  present. 

The  percentage  of  bitumen  insoluble  in  carbon  tetrachloride 
is  reported  upon  the  basis  of  total  bitumen  taken  as  100.  The 
difference  between  the  material  insoluble  in  carbon  disulphide 
and  in  carbon  tetrachloride  is  the  bitumen  insoluble  in  the 
latter.  The  method  of  calculating  results  to  be  reported  is 
illustrated  by  the  following  example,  if  the  amount  of  material 
insoluble  in  €82  is  0.1%  and  the  amount  insoluble  in  CCU  is  0.3%. 
Bitumen  insoluble  in  CC14  0.3—0.1  0.2 


Total  bitumen  TOO  —  o.i       99.9 

Value  of  the  Determination 


0.2%. 


The  presence  of  carbenes  in  petroleum  and  asphalt  products 
is  indicative  of  unnecessarily  high  temperatures  in  their  produc- 
tion. Most  carefully  prepared  petroleum  residuums  are  as  com- 
pletely soluble  in  carbon  tetrachloirde  as  in  carbon  disulphide. 
Incipient  cracking  due  to  local  overheating  or  prolonged  expo- 
sure to  high  temperatures  is  indicated  by  the  presence  of  car- 
benes, although  no  coke  or  organic  matter  insoluble  in  carbon 
disulphide  may  have  been  formed.  Where  carbenes  in  petroleum 
residuums  are  accompanied  by  an  appreciable  amount  of  organic 
matter  insoluble  in  carbon  disulphide,  indications  point  strongly 
to  injury  of  the  material  by  decomposition  of  some  of  the  hydro- 


DIMETHYL  SULPHATE  TEST  95 

carbons  present.  Some  native  asphalts,  such  as  the  Trinidad 
and  Cuban  products,  are  slightly  more  soluble  in  carbon  tetra- 
chloride  than  in  carbon  disulphide,  while  others  that  have  been 
produced  in  nature  at  relatively  high  temperatures  show  appre- 
ciable quantities  of  carbenes.  Grahamite  in  particular  may 
show  as  high  as  60  or  70  per  cent  of  carbenes.  With  the  excep- 
tion of  grahamite,  however,  the  percentage  of  carbenes  in  most 
petroleum  and  asphalt  products  for  use  in  highway  engineering 
is  commonly  specified  as  less  than  0.5%.  There  is  no  direct 
relation  which  may  be  expressed  between  the  percentage  of 
carbenes  and  other  physical  and  chemical  properties  of  a  mate- 
rial. Thus  a  fluid  petroleum  residuum  carelessly  manufactured 
may  contain  a  relatively  large  amount,  while  a  solid  residuum 
carefully  prepared  from  the  same  petroleum  may  be  entirely 
soluble  in  carbon  tetrachloride.  All  distillates  produced  by  the 
fractional  distillation  of  bituminous  materials  are  completely 
soluble  in  this  solvent.  As  a  rule,  tars  are  not  as  soluble  in 
carbon  tetrachloride  as  in  carbon  disulphide,  but  the  difference 
in  solubility  appears  to  bear  no  relation  to  the  amount  of  free 
carbon  which  is  present  in  the  tar.  In  the  routine  examination  of 
tars,  carbon  tetrachloride  is  not  employed  as  a  solvent,  and  the 
term  "carbenes"  is  therefore  limited  to  constituents  of  petroleum 
and  asphalt  products. 

DIMETHYL  SULPHATE  TEST 

Equipment. — Same  as  for  the  distillation  test,  flask  method, 
and  in  addition  3  10  cubic  centimeter  glass  cylinders,  with  ground- 
glass  stoppers,  graduated  to  0.2  cubic  centimeters. 

Method. — The  dimethyl  sulphate  test  is  used  to  detect  the 
presence  of  petroleum  or  asphalt  products  in  tars  and  is  usually 
made  upon  high  boiling  distillates  obtained  from  a  sample  of  the 
material  which  has  been  subjected  to  the  distillation  test,  flask 
method.  For  this  purpose  the  pitch  residue  which  has  been 
obtained  from  the  distillation  test,  after  cooling  and  weighing, 
is  again  heated  in  the  original  Engler  flask  and  fractions  are 
taken  at  350°  C.  and  370°  C.  These  fractions,  together  with 


96  MISCELLANEOUS    TESTS 

the  270-300°  C.  fraction  previously  obtained,  are  separately 
stirred,  and,  if  necessary,  heated  to  dissolve  solids  which  may 
be  present. 

Four  cubic  centimeters  of  distillate  from  each  fraction  are  sep- 
arately shaken  with  6  cubic  centimeters  of  dimethyl  sulphate  in 
a  10  cubic  centimeter  cylinder.  After  standing  30  minutes  any 
resulting  supernatant  layer  of  insoluble  oil  is  read  and  calculated 
to  its  percentage  by  volume  of  the  sample  of  distillate  taken. 
The  results  are  reported  as  follows: 


Fractions 

Per  cent 
distillate 

Per  cent  of  distillate 
insoluble   in   dimethyl 
sulphate 

270°  to  300°  C  

300°  to  350°  C 

^0°  to  ^7S°  C 

Great  care  should  be  exercised  in  handling  the  dimethyl 
sulphate  as  it  is  very  poisonous,  both  the  liquid  and  its  vapors 
being  extremely  irritating  to  the  skin. 

Value  of  the  Test 

Petroleum  and  asphalt  distillates  are  insoluble  in  dimethyl 
sulphate  while  tar  distillates  are  completely  soluble.  Mixed  dis- 
tillates are  therefore  only  partially  soluble.  Sufficiently  high 
boiling  distillates  are  tested  to  insure  the  presence  of  fractions 
of  the  petroleum  or  asphalt  product  if  either  is  present.  The 
test  is  mainly  qualitative,  but  is  valuable  when  as  little  as  3 
per  cent  of  petroleum  or  asphalt  products  are  present  in  the  tar. 


MISCELLANEOUS  TESTS 

FIXED   CARBON  AND  ASH 

Equipment: 

i  iron  ring  support  (ring  7.5  cm.  in  diameter), 
i  platinum  or  nichrome  triangle, 
i  Bunsen  burner  and  rubber  tubing. 


PIXED    CARBON    AND    ASH 


97 


i  platinum  crucible  with  a  tight-fitting  cover  (weight  com- 
plete, from  20  to  30  grams). 

i  crucible  tongs. 

i  desiccator  with  calcium  chloride. 

i  analytical  balance,  capacity  100  grams,  sensitive  to  o.i 

milligram. 

Method. — This  is  a  purely  arbitrary  test  for  bituminous  mate- 
rials which  has  been  borrowed  from  the  ordinary  methods  for  coal 
analysis.  Described  here  somewhat  more  in  detail,  it  is  the  same 
as  that  adopted  by  The  American  Society  for  Testing  Materials  in 
1911.  The  determination  is  made  in  accordance  with  the  method 
described  for  coal  in  the  Journal 
of  the  American  Chemical  Society, 
1899,  Volume  21,  page  1116.  One 
gram  of  the  material  is  placed  in  a 
platinum  crucible  weighing  from 
20  to  30  grams  and  having  a  tight- 
ly fitting  cover.  It  is  then  heated 
for  seven  minutes  over  the  full 
flame  of  a  Bunsen  burner,  as  shown 
in  Fig.  29.  The  crucible  should  be 
supported  on  a  platinum  or  nich- 
rome  triangle  with  the  bottom 
from  6  to  8  centimeters  above  the 
top  of  the  burner.  The  flame 
should  be  fully  20  centimeters  high 
when  burning  freely,  and  the  de- 
termination should  be  made  in  a 
place  free  from  drafts.  The  upper 

surface  of    the  COVer   should   burn   FlG'  29'     Apparatus  for  Determi- 

nation  of  Fixed  Carbon 

clear,  but  the  under  surface  should 

remain  covered  with  carbon,  excepting  in  the  case  of  some  of 
the  more  fluid  bitumens,  when  the  under  surface  of  the  cover 
may  be  quite  clean. 

The  crucible  is  removed  to  a  desiccator  and  when  cool  is 
weighed,  after  which  the  cover  is  removed,  and  the  crucible  is 
placed  in  an  inclined  position  over  the  Bunsen  burner  and 


98  FIXED    CARBON    AND    ASH 

ignited  until  nothing  but  ash  remains.  Any  carbon  deposited 
on  the  cover  is  also  burned  off.  The  weight  of  the  ash  remain- 
ing is  deducted  from  the  weight  of  the  residue  after  the  first 
ignition  of  the  sample.  This  gives  the  weight  of  the  so-called 
fixed  or  residual  carbon,  which  is  calculated  on  a  basis  of  the 
total  weight  of  the  sample,  exclusive  of  mineral  matter.  Thus, 
if  a  one-gram  sample  yields  upon  the  first  heating  0.13  grams 
residue  and  after  final  ignition  0.03  grams  of  ash,  the  percentage 
of  fixed  carbon  is  calculated  as  follows: 

=  10.72% 


i.oo  —  0.03       0.97 

If  the  presence  of  a  carbonate  mineral  is  suspected,  the 
percentage  of  mineral  matter  may  be  most  accurately  obtained 
by  treating  the  ash  with  a  few  drops  of  ammonium  carbonate 
solution,  drying  at  100°  C.,  then  heating  for  a  few  minutes  at 
a  dull-red  heat,  cooling  and  weighing. 

An  excellent  form  of  crucible  for  this  test  is  shown  in  Fig.  29. 
It  has  a  cover  with  a  flange  4  millimeters  wide,  fitting  tightly 
over  the  outside  of  the  crucible,  and  weighs  complete  about  25 
grams.  Owing  to  sudden  expansion  in  burning  some  of  the  more 
fluid  bitumens,  it  is  well  to  hold  the  cover  down  with  the  end 
of  the  tongs  until  the  most  volatile  products  have  burned  off. 

Some  products,  particularly  those  derived  from  Mexican 
petroleum,  show  a  tendency  to  suddenly  expand  and  foam  over 
the  sides  of  the  crucible  in  making  this  determination,  and  no 
method  of  obviating  this  trouble  without  vitiating  the  result 
has  thus  far  been  forthcoming.  Recent  experiments  in  the  lab- 
oratory of  the  Office  of  Public  Roads  and  Rural  Engineering 
indicate  that  the  difficulty  may  in  many  cases  be  overcome  by 
placing  a  small  piece  of  platinum  gauze  over  the  sample  and 
about  midway  of  the  crucible.  The  gauze  should  be  so  cut  or 
bent  as  to  touch  the  sides  of  the  crucible  at  all  points,  and  is 
of  course  weighed  in  place  in  the  crucible  before  and  after 
ignition. 


VALUE    OF    THE    FIXED    CARBON    DETERMINATION  99 

Value  of  the  Test 

To  be  of  any  real  value  the  fixed  carbon  determination  should 
be  made  exactly  as  described  in  the  preceding  paragraphs.  It  is 
not  an  exceedingly  accurate  test,  and  any  attempt  at  variation 
in  the  method  of  heating  or  other  conditions  specified  will  often 
greatly  affect  the  results  obtained.  When  properly  made,  the 
fixed  carbon  test  may  serve  as  a  means  of  identifying  the  type 
of  petroleum  from  which  a  fluid  or  semisolid  residuum  has  been 
manufactured.  Paraffin  petroleums  and  all  petroleum  distillates 
yield  little  or  no  fixed  carbon.  Asphaltic  petroleums  and  their 
residual  products  always  yield  fixed  carbon,  but  in  varying 
amounts,  according  to  their  origin  or  method  of  manufacture. 
For  a  given  viscosity,  float  test,  or  penetration,  blown  petroleums 
show  a  very  low  percentage  of  fixed  carbon  and  straight  distilled 
Mexican  petroleum  residuums  a  relatively  high  percentage. 
For  any  type  of  petroleum  residuum,  fixed  carbon  increases  as 
distillation  progresses.  It  is  therefore  accompanied  by  increase 
in  specific  gravity,  percentage  of  asphaltenes,  viscosity  and  float 
test,  and  decrease  in  penetration.  Native  asphalts  usually  yield 
from  ii  to  15  per  cent  of  fixed  carbon,  although  the  harder 
varieties  sometimes  run  considerably  higher,  and  in  the  case  of 
grahamite  may  reach  50  per  cent  or  over.  The  test  is  seldom 
applied  to  tars,  or  tar  products,  owing  to  the  presence  of  free 
carbon  which  interferes  with  the  determination.  If  made  upon 
tars,  the  weight  of  free  carbon  in  the  one-gram  sample  should  be 
determined  by  test  and  deducted  from  the  weight  of  residue 
from  the  first  heating  before  calculating  the  percentage  of  fixed 
carbon. 

In  interpreting  the  fixed  carbon  determination  it  should  be 
remembered  that  the  fixed  carbon  is  actually  produced  from  the 
material  by  d^tructive  distillation  and  does  not  exist  as  such 
in  the  original  material.  It  is  therefore  quite  distinct  from  free 
carbon,  which,  if  determined  to  exist  at  all,  is  actually  present 
in  the  original  material  and  is  merely  separated  from  the  other 
constituents  by  means  of  a  solvent. 

The  amount  and  character  of  the  ash  often  serves  as  an  aid  to 


100  PARAFFIN    SCALE    DETERMINATION 

identification  of  the  material.  Thus  petroleum  products  seldom 
yield  more  than  0.2  and  usually  less  than  o.i  per  cent  ash,  while 
the  native  asphalt  products  yield  considerably  more,  in  certain 
cases  running  over  30  per  cent.  Moreover,  the  ash  of  many  of 
the  native  asphalts  shows  a  characteristic  color  and  texture. 

PARAFFIN   SCALE   DETERMINATION 

Equipment : 

one-half  pint  iron  retort.     (Fig.  30.) 
piece  iron  tubing,  30  inches  long. 
100  cubic  centimeter  Erlenmeyer  flasks. 

500  cubic  centimeter    (16-02.)  flask,  with  side  neck  for  filtering  under 
pressure. 

freezing  apparatus.     (Fig.  31.) 
6-inch  test  tube,  ^-inch  diameter. 

analytical  balance,  capacity  100  grams,  sensitive  to  o.i  milligram, 
rough  balance,  capacity  I  kilogram,  sensitive  to  o.i  gram, 
wash  bottle, 
pint  tin  cup,  seamless, 
vacuum  pump  and  connections, 
glass  crystallizing  dish,  50  millimeters  in  diameter, 
steam  bath. 

desiccator  with  calcium  chloride. 
4-inch  steel  spatula. 
Bunsen  burner  with  rubber  tubing. 
2  iron  stands  with  retort  clamp,  and  I  ring. 

Method. — Fifty  grams  of  the  material  under  examination  should  be  weighed 
into  the  tared  iron  retort  as  shown  in  Fig.  30,  and  distilled  as  rapidly  as  possible 
to  dry  coke.  The  distillation  should  be  complete  in  not  over  25  minutes.  The 
distillate  is  caught  in  a  100  cubic  centimeter  Erlenmeyer  flask,  the  weight  of 
which  has  been  previously  ascertained.  During  the  early  stages  of  distillation 
a  cold,  damp  towel  wrapped  around  the  stem  of  the  retort  will  serve  to  con- 
dense the  distillate.  After  high  temperatures  have  been  reached,  this  towel 
may  be  removed.  When  the  distillation  is  completed  the  distillate  is  allowed 
to  cool  to  room  temperature  and  is  then  weighed  in  the  flask.  This  weight 
minus  that  of  the  flask  gives  the  weight  of  the  total  distillate. 

The  apparatus  for  freezing  out  and  separating  the  paraffin  scale  is  shown  in 
Fig.  31.  It  consists  of  a  bell  jar  about  16  centimeters  high  and  14  centimeters 
in  diameter,  surrounded  by  a  felt  or  cotton  cover,  b.  A  copper  jacket,  c,  4^ 
centimeters  in  diameter  at  the  top  and  21  centimeters  long,  is  held  in  the  neck 
of  the  bell  jar  by  means  of  a  rubber  stopper,  d,  and  fits  into  the  upper  portion  of 
the  rubber  stopper,./.  A  glass  filter  tube,  e,  fits  inside  the  copper  jacket,  and  to 
prevent  circulation  of  air  and  condensation  of  water  between  it  and  the  jacket  a 
strip  of  heavy  blotting  paper,  /,  is  wrapped  around  the  top  of  the  filter  tube. 
Just  below  the  constriction  in  the  filter  tube  a  wad  of  absorbent  cotton,  g,  is 
placed,  tightly  compressed  to  a  length  of  2  centimeters  by  means  of  a  glass  rod. 
Above  this  is  a  wad  of  tightly  packed  asbestos  wool,  h,  about  5  millimeters  in 
length,  upon  which  an  asbestos  filtering  mat,  i,  is  prepared.  The  filter  tube 
passes  through  a  rubber  stopper,.;,  into  a  vacuum  filtering  flask,  k,  of  500  cubic 
centimeters  capacity.  The  rubber  stopper,  j,  is  placed  as  tightly  as  possible 
against  the  neck  of  the  bell  jar,  but  to  insure  that  there  is  no  circulation  of  air  a 
disk  of  blotting  paper,  /,  is  compressed  between  them.  The  thermometer,  m,  is 
capable  of  recording  temperatures  from  —  25°  C.  to  o°C.  and  has  the  —  20°  C. 
graduation  at  least  14  centimeters  from  the  bulb.  It  is  supported  by  means  of 


PARAFFIN    SCALE    DETERMINATION 


101 


a  guiding  cork,  «,  and  cork  disk,  0,  which  is  held  tightly  against  the  top  of 
the  filter  tube  by  the  clamp,  p. 

The  bell  jar  is  filled  with  a  freezing  mixture  of  ice  and  salt  in  the  proportion 
of  three  to  one,  which,  as  it  melts,  is  drawn  off  through  the  bent  glass  tube,  q, 
which  is  fitted  with  a  rubber  connection,  r,  and  pinch  cock,  5,  and  collected  in 
the  500  cubic  centimeter  filtering  flask,  /.  The  apparatus  is  supported  on  the 
ring,  u,  and  condenser  clamp,  v,  attached  to  the  stand,  w. 

In  separating  the  paraffin  scale  the  following  procedure  is  carried  out. 
The  filtering  flask,  k,  is  removed  and  a  small  cork  stopper  inserted  in  the  lower 
end  of  the  filter  tube  to  assist  in  retaining  the  solution  to  be  chilled  in  the  upper 
part  of  the  tube.  Ten  cubic  centimeters  of  a  mixture  of  equal  parts  Squibbs' 


FIG.  30.     Distillation  Apparatus  for  Paraffin  Scale  Determination 

ether  and  absolute  alcohol  is  poured  into  the  filter  tube,  the  temperature  of 
which  has  been  reduced  to  —20°  C.  From  one  to  two  grams  of  the  well-mixed 
distillate  obtained  in  the  manner  previously  described  is  then  accurately 
weighed  in  a  100  cubic  centimeter  Erlenmeyer  flask,  mixed  with  10  cubic 
centimeters  of  Squibbs'  ether,  and  poured  into  the  filter  tube.  Ten  cubic 
centimeters  of  absolute  alcohol  is  next  placed  in  the  flask  to  wash  out  the 
ether  solution,  poured  into  the  filter  tube,  and  the  cover  carrying  the  thermom- 
eter placed  on  the  tube.  The  mixture  is  maintained  at  a  temperature 
—20°  C.  for  15  minutes,  then  the  cork  stopper  is  removed  from  the  outlet  of  the 
filter  tube  and  the  filtering  flask  is  replaced.  The  corks  supporting  the  ther- 
mometer are  now  loosened  and  a  strong  suction  is  applied  to  the  filter  flask 
until  all  of  the  solvent  is  drawn  off.  The  contents  of  the  filter  tube  are  next 
washed  with  10  cubic  centimeters  of  a  I  to  I  mixture  of  Squibbs'  ether  and 
absolute  alcohol,  which  is  chilled  to  —  20°  C.  in  the  filter  tube  before  suction  is 
applied.  When  the  washings  have  been  removed  the  vacuum  is  turned  off 
and  the  filter  tube  removed  from  the  apparatus.  The  filter  tube  is  then 
placed  in  a  clean  filter  flask  which  also  contains  a  6-inch  test  tube  in  which  the 
dissolved  paraffin  scale  is  later  collected.  About  10  cubic  centimeters  of  warm 
petroleum  ether  are  poured  into  the  filter  tube  and  allowed  to  remain  until  the 
paraffin  scale  has  been  dissolved.  Vacuum  is  then  applied  and  the  dissolved 


102 


PARAFFIN    SCALE    DETERMINATION 


scale  drawn  into  the  test  tube.  This  treatment  is  followed  by  two  washings, 
one  of  10  cubic  centimeters  and  the  other  of  5  cubic  centimeters  of  warm 
petroleum  ether,  which  removes  the  last  traces  of  paraffin  scale.  The  entire 
contents  of  the  test  tube  are  then  poured  into  a  weighed  platinum  or  glass 
crystallizing  dish  and  the  petroleum  ether  evaporated  off  over  a  steam  bath. 
The  dish  is  then  placed  in  a  drying  oven  maintained  at  105°  C.  until  the  last 


FlG.  31.     Filtration  Apparatus  for  Paraffin  Scale  Determination 

traces  of  petroleum  ether  have  been  removed  and  the  paraffin  scale  has  at- 
tained a  constant  weight,  after  cooling  in  a  desiccator. 

The  weight  of  the  paraffin  scale  so  obtained  divided  by  the  weight  of  the 
distillate  taken  and  multiplied  by  the  percentage  of  the  total  distillate  obtained 
from  the  original  sample  equals  the  percentage  of  the  paraffin  scale.  Thus,  if 
50  grams  of  the  material  produces  30  grams  of  distillate  and  this  distillate 
yields  2.0  per  cent  paraffin  scale,  the  percentage  of  paraffin  scale  upon  the 
basis  of  the  original  sample  would  be  as  follows: 


Per  Cent  Paraffin  Scale  =  — 


=  1.2% 


SPECIAL    TESTS    FOR    EMULSIONS  103 

Value  of  Determination 

When  made,  this  determination  is  confined  to  petroleum  and 
asphalt  products.  It  is  not  a  thoroughly  reliable  quantitative 
determination,  as  unavoidable  slight  variations  in  the  method 
and  rate  of  distillation  cause  wide  variations  in  results.  More- 
over, it  appears  likely  that  solid  paraffins  may  be  both  destroyed 
and  formed  during  the  process  of  destructive  distillation. 

Owing  to  the  fact  that  it  is  subject  to  wide  variations  it  is 
of  doubtful  value  except  as  a  very  roughly  quantitative  test  for 
the  purpose  of  identification.  By  some  the  presence  of  solid 
paraffins  in  a  bituminous  material  for  use  in  highway  engineering 
is  believed  to  be  undesirable.  While  it  is  true  that  those  petro- 
leum products  in  which  paraffin  hydrocarbons  greatly  predomi- 
nate are  unsuited  for  use  as  cementing  mediums,  and  while  a 
high  percentage  of  liquid  paraffin  hydrocarbons  is  often  indicated 
by  the  presence  of  an  appreciable  amount  of  paraffin  scale,  it 
does  not  follow  that  the  latter  are  themselves  entirely  undesir- 
able constituents.  In  fact,  if  the  material  in  which  they  occur 
possesses  the  requisite  degree  of  cementitiousness,  the  presence 
of  solid  paraffins  may  make  the  material  more  chemically  stable 
than  it  otherwise  would  be.  There  appears  to  be  a  general  ten- 
dency to  eliminate  the  paraffin  scale  clause  in  specifications  for 
bituminous  materials  for  the  reason  above  stated.  Most  as- 
phaltic  petroleums  and  native  asphalts  contain  only  traces  of 
paraffin  scale,  while  the  semi-asphaltic  type  shows  comparatively 
small  amounts. 


SPECIAL  TESTS  FOR  EMULSIONS 

The  exact  determination  of  the  constituents  of  a  bituminous 
emulsion  is  usually  attended  with  considerable  difficulty  and  no 
predetermined  scheme  can  be  made  applicable  to  all  materials 
of  this  character.  The  following  methods,  however,  are  used 
by  the  United  States  Office  of  Public  Roads  and  Rural  Engineer- 
ing and  have  yielded  satisfactory  and  fairly  accurate  results: 


104  SPECIAL    TESTS    FOR    EMULSIONS 

Eatty  and  Resin  Acids 

In  order  to  break  up  the  emulsion,  a  2O-gram  sample  is  digested  on  a  steam 

N 
bath  with  100  cubic  centimeters  of\^  —  alcoholic  potash.     The  digestion  is 

carried  out  in  a  flask  with  a  reflux  condenser  for  about  45  minutes.  The 
solution  is  filtered  and  the  precipitate  washed  with  95  per  cent  alcohol.  The 
filtrate  is  evaporated  to  dryness,  after  which  the  residue  is  taken  up  with  hot 
water  and  any  insoluble  matter  is  filtered  off.  The  aqueous  solution,  which 
contains  the  potassium  soaps  of  the  fatty  acids,  is  acidified  with  dilute  sul- 
phuric acid  and  then  shaken  in  a  separately  funnel  with  petroleum  ether. 
The  aqueous  portion  is  drawn  off  and  the  ethereal  layer  shaken  up  with  cold 
water  and  washed  twice,  after  which  it  is  evaporated  in  a  weighed  platinum  or 
porcelain  dish  to  constant  weight,  first  over  a  steam  bath  and  then  in  a  drying 
oven  at  105°  C.  The  residue  consists  of  the  fatty  and  resin  acids  present  in  the 
emulsion. 

Water 

The  percentage  of  water  in  the  emulsion  is  determined  by  distilling  a  100- 
gram  sample  in  the  retort  used  for  dehydration.  The  distillation  is  carried  out 
in  exactly  the  same  manner  as  described  under  this  test  until  the  volume  of 
water  in  the  receiver  shows  no  further  increase.  Any  oils  that  come  over  are 
thoroughly  mixed  with  the  material  remaining  in  the  retort. 

Ammonia 

Many  emulsions  contain  ammonia,  and  when  this  is  present  a  second 
distillation  of  the  material  is  necessary.  This  is  carried  out  on  a  loo-gram 
sample  in  exactly  the  same  manner  as  described  for  the  determination  of  water, 
except  for  the  fact  that  40  cubic  centimeters  of  a  10  per  cent  solution  of 
caustic  potash  is  added  to  the  contents  of  the  retort  before  beginning  the  dis- 
tillation. The  distillate  is  collected  in  a  measured  volume  of  —  sulphuric 

N 
acid.     When  the  distillation  is  completed  the  excess  of  acid  is  titrated  with  — 

caustic  potash,  and  the  ammonia  thus  determined. 

Ash 

A  one-gram  sample  of  the  dehydrated  material  is  ignited  in  a  weighed 
platinum  or  porcelain  crucible.  The  ash  will  contain  any  inorganic  matter 
from  the  bitumen  as  well  as  the  fixed  alkali  present  in  the  soap.  The  results 
are,  of  course,  all  calculated  on  the  basis  of  the  original  material. 

Total  Bitumen 

A  two-gram  sample  of  dehydrated  material  is  extracted  with  carbon  disul- 
phide  as  described  in  the  method  for  the  determination  of  total  bitumen, 
flask  method,  and  in  this  manner  the  organic  matter  insoluble  in  carbon 
disulphide  can  be  determined. 

Having  determined  all  constituents  as  above  noted,  it  is  assumed  that  the 
difference  between  their  sum  and  100  per  cent  is  bitumen,  which  amount  is  re- 
ported accordingly. 

SOLUBILITY  IN  BENZOL  OR  CHLOROFORM 

Hot  Extraction 

A  hot  extraction  of  a  bituminous  material  may  be  made  with  any  volatile 
solvent  but,  with  the  exception  of  creosoting  oils  and  to  some  extent  bitumi- 
nous aggregates,  cold  extractions  or.  those  made  at  room  temperature  as  de- 


SOLUBILITY    IN    BENZOL    OR    CHLOROFORM 


105 


scribed  under  the  determinations  for  total  bitumen,  asphaltenes  and  carbenes, 
are  in  more  general  use  for  materials  directly  used  in  highway  engineering. 
While  the  total  bitumen  determination  is  for  many  reasons  to  be  preferred  as  a 
single  solvent  test  for  creosoting  oils,  solvents  other  than  carbon  disulphide 
have  been  used  for  so  long  a  time  that  most  specifications  for  creosoting  oils 
fail  to  include  their  solubility  in  carbon  disulphide  and  require  a  test  with 
benzol  or  chloroform,  or  both. 

There  are  many  types  of  hot  extraction  apparatus  and  a  number  of  varia- 
tions in  methods  of  making  the  extraction.  All  of  the  hot  extraction  methods 
are,  however,  the  same  in  general  principle,  and  the  fol- 
lowing method  substantially  as  recommended  in  1915  by 
the  Special  Committee  on  Road  Materials  of  The  Ameri- 
can Society  of  Civil  Engineers  may  be  considered  as 
illustrative.  Fig.  32  shows  one  type  of  extraction  appa- 
ratus. In  this  apparatus  the  solvent  is  continuously 
boiled  in  the  bottom  of  the  glass  receptacle  and  con- 
densed at  the  top.  The  material  to  be  extracted  is  held 
above  the  main  mass  of  solvent  in  a  filter  suspended  in 
a  wire  frame,  but  during  the  test  remains  in  an  at- 
mosphere of  the  solvent  vapor  and  is  acted  upon  by  the 
condensedfportions  of  the  solvent  in  finding  their  way^back 
to  the  main  mass.  The  solvent  is  thus  used  over  and  over 
while  the  soluble  portion  accumulates  in  the  bottom  of 
the  receptacle. 

From  5  to  10  grams  of  the  water-free  oil  is  weighed 
out  into  a  weighed  loo-c.c.  beaker.  Fifty  c.c.  of  the  sol- 
vent are  added,  and  the  solution  is  passed  through  a 
weighted  9-cm.  C.  S.  &  S.  No.  575  filter  paper  in  a  short- 
stemmed  funnel  or  an  alundum  crucible,  the  filtrate  be- 
ing passed  into  the  flask  to  be  subsequently  used  for  the 
hot  extraction.  The  beaker  is  washed  clean  from  all 
soluble  matter,  dried,  and  weighed.  The  filter  paper  or 
crucible  and  contents  are  then  placed  in  the  extraction 
apparatus,  and  heat  is  applied  from  a  water  bath  or  hot 
plate  until  the  extracton  is  complete  and  the  filtrate 
runs  through  colorless.  The  filter  and  contents  are  then 
dried  in  a  hot-air  oven  at  about  90°  C,  cooled  in  a  des- 
iccator, and  weighed.  The  increase  in  weight  is  added 
to  the  increase  in  weight  of  the  beaker,  if  any,  the  re- 
sult being  the  weight  of  the  insoluble  matter.  The 
weight  of  the  insoluble  matter  thus  found  is  subtracted 
from  the  weight  of  the  material  taken  for  analysis.  The 

difference  in  weight  is  the  weight  of  the  soluble  matter,  from  which  the  per- 
centage is  calculated.  If  a  filter  paper  is  used  in  this  test  it  is  advisable  to  first 
soak  it  in  the  solvent  to  remove  any  grease  which  it  may  hold  and  then  dry, 
cool  and  weigh  it  in  exactly  the  same  manner  as  will  be  used  after  the  ex- 
traction is  complete. 


FIG.  32.     Hot 
Extractor 


SPECIAL  TESTS  FOR  CREOSOTING  OILS 

The  following  tests  are  slightly  modified  from  descriptions 
by  Church.*  They  are  roughly  quantitative  and  are  not  sus- 
ceptible to  a  great  degree  of  refinement. 


*  Methods  for  Testing  Coal  Tar  and  Refined  Tars,  Oils  and  Pitches  Derived  Therefrom. 
Jour.  Ind.  and  Eng.  Chem.    Vol.  3,  p.  227. 


106 


TAR  ACIDS   AND   NAPHTHALENE 


Tar  Acids 

One  hundred  cubic  centimeters  of  the  material  are  weighed  into  an  Engler 
distilling  flask,  which  is  then  set  up  as  shown  in  Fig.  33.  Heat  is  applied  so 
that  the  distillate  comes  over  at  the  rate  of  about  5  cubic  centimeters  per 
minute.  Distillation  may  be  stopped  when  the  thermometer  reaches  355°  C. 
When  distilling  distillate  oils,  Church  carries  the  distillation  to  a  point  where 
at  least  95  per  cent  has  distilled  off.  The  condenser  tube  is  kept  sufficiently 
warm,  by  means  of  a  burner  if  necessary,  to  prevent  solidification  of  the  dis- 
tillate. The  total  distillate  is  collected  in  a  special  graduated  form  of  separa- 
tory  funnel. 

After  distillation  the  separatory  funnel  and  contents  are  warmed  in  water 
to  60°  C.  and  the  volume  noted.  Fifty  cubic  centimeters  of  a  ten  per  cent 
caustic  soda  solution  are  then  added  and  the  whole  well  shaken.  The  mixture 


FIG.  33.     Distillation  Apparatus  for  Determination  of  Tar  Acids 

is  then  allowed  to  settle,  the  clear  soda  solution  drawn  off  and  the  contents 
of  the  funnel  again  warmed  to  60°  C.  and  the  volume  is  read.  If  a  shrinkage 
from  the  first  reading  is  noted,  30  cubic  centimeters  of  the  soda  solution  are 
added  and  the  operation  repeated  until  no  further  shrinkage  in  volume  is  noted 
between  the  last  two  readings.  The  total  shrinkage  in  cubic  centimeters 
divided  by  the  original  volume  of  distillate  is  taken  as  the  percentage  of  tar 
acids  in  the  distillate.  This  percentage  may  then  be  figured  upon  the  basis 
of  the  original  material  by  correcting  the  original  recorded  volume  of  the 
distillate  to  normal  temperature.  For  this  purpose  the  original  volume  of 
distillate  may  be  divided  by  1.028. 

Dry  Naphthalene 

The  extracted  distillate  from  the  determination  of  tar  acids  is  placed  in  a 
copper  beaker  and  maintained  at  15.5°  C.  for  15  minutes.  The  material  is  then 
filtered  in  a  funnel  fitted  with  a  filter  cone  and  vacuum  applied  until  no  more 
oil  is  removed.  Any  naphthalene  in  the  filter  is  then  pressed  between  paper  in 
a  letter  press  to  remove  as  much  of  the  absorbed  oil  as  possible,  after  which 
it  is  weighed  and  its  percentage  figured  on  the  weight  of  original  material 
which  was  distilled  in  the  determination  of  tar  acids. 


SULPHONATION    TEST 


107 


Sulphonation  Test 

Two  hundred  cubic  centimeters  of  the  material  is  weighed  into  a  soo-cc. 
Jena  flask,  which  is  then  set  up  as  shown  in  Fig.  34.  Distillation  is  carried  to 
320°  C.  and  the  distillate  from  305°  to  320°  C.  is  caught  in  a  tared  receiver  and 
its  weight  ascertained.  The  weighed  fraction  is  then  warmed  to  60°  C.  with 
from  four  to  five  times  its  volume  of  concentrated  sulphuric  acid,  and  the 
whole  transferred  to  a  special  graduated  form  of  separatory  funnel. 
(See  Fig.  22.)  The  receiver  is  rinsed  three  times  with  concentrated  sulphuric 
acid  and  the  rinsings  added  to  the  contents  of  the  funnel. 

The  funnel  is  then  stoppered  and  shaken,  first  cautiously,  then  vigorously, 
for  about  15  minutes  and  the  contents  allowed  to  settle  overnight.  The  acid 
is  then  carefully  drawn  down  into  the  graduated  portion  of  the  funnel  to  within 


Thermometer 


Condenser 


FIG.  34.     Distillation  Apparatus  for  Sulphonation  Test 

2  cubic  centimeters  of  any  unsulphonated  residue.  Whether  or  not  any  un- 
sulphonated  residue  is  visible,  the  test  is  carried  further  by  adding  about  20 
cubic  centimeters  of  water  and  allowing  it  to  settle  for  one  half-hour.  The 
water  is  then  drawn  down  as  close  as  possible  without  removing  any  super- 
natant oil  or  emulsion.  Ten  cubic  centimeters  of  strong  sulphuric  acid  are  next 
added  and  allowed  to  settle  for  from  15  to  20  minutes.  Any  unsulphonated 
residue  should  now  settle  out  clear  and  give  a  distinct  reading.  If  it  amounts 
to  less  than  0.2  cubic  centimeter  it  should  be  drawn  down  into  the  narrow  part 
of  the  funnel  just  above  the  stopcock,  where  it  may  be  estimated  to  o.oi  cubic 
centimeter.  The  number  of  cubic  centimeters  is  figured  as  percentages  on 
the  weight  of  the  fraction  taken.  Thus  if  the  original  fraction  weighs  10 
grams  and  0.5  cubic  centimeter  of  unsulphonated  residue  remains,  this 
residue  is  reported  as  5  per  cent  of  the  fraction. 

If  the  unsulphonated  oil  is  dark  in  color  it  should  be  treated  with  an  excess 
of  10  per  cent  sodium  hydroxide  solution.  If  the  oil  is  soluble  in  this  reagent 
the  test  is  regarded  as  negligible. 


108  CENTRIFUGAL    EXTRACTION 

EXTRACTION   OF   BITUMINOUS   AGGREGATES   AND 
RECOVERY  OF  BITUMEN  AND  AGGREGATE 

CENTRIFUGAL   EXTRACTION 

Equipment: 

i  centrifuge  extractor,  complete  with  motor,  speed  regu- 
lator, and  electrical  connections. 

i  hot  plate. 

i  tin  dish  approximately  2  inches  deep  and  9  inches  in 
diameter. 

i  hammer. 

i  J^-inch  cold  chisel. 

i  large  metal  kitchen  spoon. 

i  square  foot  of  /{e-inch  deadening  felt  paper. 

i  i^-inch  stiff  flat  brush. 

i  500  cubic  centimeter  bottle  or  flask. 

i  balance,  capacity  i  kilogram,  sensitive  to  o.i  gram. 

i  sheet  of  heavy  manila  paper. 

Method. — There  are  two  types  of  centrifugal  extractors  for 
bituminous  materials  in  general  use  which  are  similar  in  design, 
the  Reeve  type  and  the  Dulin.  The  latter  is  made  in  two 
sizes,  one  primarily  for  coarse  aggregates  and  the  other  for 
the  extraction  of  fine  aggregates  such  as  sheet  asphalt  topping 
when  it  is  desired  to  recover  the  mineral  matter  for  further 
test.  The  former,  shown  in  Fig.  35,  was  designed  upon  lines 
suggested  by  an  examination  of  machines  in  use  by  A.  E.  Schutte 
and  C.  N.  Forrest.  It  consists  of  a  %-horsepower,  noo 
revolutions  per  minute,  vertical-shaft,  electric  motor,  a,  with  the 
shaft  projecting  into  the  cylindrical  copper  box,  b,  the  bottom 
of  which  is  so  inclined  as  to  drain  to  the  spout,  c.  A  3/l6- 
inch  circular  brass  plate  gJ/2  inches  in  diameter  is  shown 
in  d,  and  upon  this  rests  the  sheet-iron  bowl,  e}  which  is 
8^2  inches  in  diameter  by  2  5/l6  inches  high,  and  has  a  2 -inch 
circular  hole  in  the  top.  Fastened  to  the  inner  side  of  the 
bowl  is  the  brass  cup,  /,  having  a  circle  of  j/^-inch  holes. 


CENTRIFUGAL    EXTRACTION 


109 


for  the  admission  of  the  solvent,  and  terminating  in  the  hollow 
axle,  which  fits  snugly  through  a  hole  at  the  center  of  the  brass 
plate.  The  bowl  may  be  drawn  firmly  against  a  felt-paper  ring, 
g,  J4  mch  wide,  by  means  of  the  2J/2-mch  milled  nut,  h, 
for  which  the  hollow  axle  is  threaded  for  a  distance  of  ^ 
inch  directly  below  the  upper  surface  of  the  plate.  The  axle 
fits  snugly  over  the  shaft  of  the  motor,  to  which  it  is  locked  by  a 
slot  and  cross  pin  i. 

The  aggregate  is  prepared  for  analysis  by  heating  it  in  a  tin 
dish  on  the  hot  plate  until  it  is  sufficiently  soft  to  be  thoroughly 


FIG.  35.     Centrifugal  Extractor 
(Reeve  Type) 

disintegrated  by  means  of  a  large  spoon.  Care  must  be  taken, 
however,  that  the  individual  particles  are  not  crushed.  If  a 
section  of  pavement  is  under  examination,  a  piece  weighing 
somewhat  over  i  kilogram  may  be  cut  off  with  hammer  and 
chisel.  The  disintegrated  aggregate  is  then  allowed  to  cool, 
after  which  a  sufficient  amount  is  taken  to  yield  on  extraction 
from  50  to  60  grams  of  bitumen.  It  is  placed  in  the  iron  bowl 
and  a  ring  ^  inch  wide,  cut  from  the  felt  paper,  is  fitted 
on  the  rim,  after  which  the  brass  plate  is  placed  in  posi- 
tion and  drawn  down  tightly  by  means  of  the  milled  nut.  If 
the  bitumen  is  to  be  recovered  and  examined,  the  felt  ring  should 
be  previously  treated  in  the  empty  extractor  with  a  couple  of 
charges  of  carbon  disulphide  in  order  to  remove  any  small 
amount  of  grease  or  resin  that  may  be  present,  although  a 


110  CENTRIFUGAL    EXTRACTION 

proper  grade  of  felt  should  be  practically  free  from  such  prod- 
ucts. The  bowl  is  now  placed  on  the  motor  shaft  and  the  slot 
and  pin  are  carefully  locked.  An  empty  bottle  is  placed  under 
the  spout  and  150  cubic  centimeters  of  carbon  disulphide  are 
poured  into  the  bowl  through  the  small  holes.  The  cover  is 
put  on  the  copper  box  and,  after  allowing  the  material  to  digest 
for  a  few  minutes,  the  motor  is  started,  slowly  at  first  in  order 
to  permit  the  aggregate  to  distribute  uniformly.  The  speed 
should  then  be  increased  sufficiently  by  means  of  the  regulator 


FIG.  36.     Dulin  Rotarex 
(Small  Size) 

to  cause  the  dissolved  bitumen  to  flow  from  the  spout  in  a  thin 
stream.  When  the  first  charge  has  drained,  the  motor  is  stopped 
and  a  fresh  portion  of  disulphide  is  added.  This  operation  is 
repeated  from  four  to  six  times  with  150  cubic  centimeters  of 
disulphide. 

With  a  little  experience  the  operator  can  soon  gauge  exactly 
what  treatment  is  necessary  for  any  given  material.  When 
the  last  addition  of  solvent  has  drained  off,  the  bowl  is  re- 
moved and  placed  with  the  brass  plate  uppermost  on  a  sheet 
of  manila  paper.  The  brass  plate  and  felt  ring  are  carefully 
laid  aside  on  the  paper  and,  when  the  aggregate  is  thoroughly 
dry,  it  can  be  brushed  on  a  pan  of  the  rough  balance  and  weighed. 
The  difference  between  this  weight  and  the  original  weight  taken 


HOT    EXTRACTION 


111 


shows  the  amount  of  bitumen  extracted.     The  aggregate  may 
then  be  tested  as  occasion  requires. 

The  operation  of  the  Dulin  Rotarex  shown  in  Fig.  36  is 
practically  identical  with  that  above  described. 


HOT  EXTRACTION 

Equipment. — Same  as  for  centrifugal  extraction  except  that 
a  New  York  Testing  Laboratory  hot  extractor,  complete  with 
electric-light  bulb,  electrical  and  cold-water  connections,  replaces 
the  centrifugal  extractor. 

Method. — The  New  York  Testing  Laboratory  extractor  shown 
in  Fig.  37  consists  of  a  large  brass  cylinder,  through  the  bottom 
of  which  projects  a  i6-candle-power  incandescent  carbon-filament 


FIG.  37.     New  York  Testing  Laboratory  Hot  Extractor 

bulb  to  supply  heat  to  the  extraction  apparatus  proper,  which 
is  held  in  the  upper  portion  of  the  cylinder.  This  apparatus 
is  composed  of  a  cylindrical  brass  vessel  for  holding  the  solvent, 
a  cylindrical  wire  basket  made  of  8o-mesh  wire  cloth,  suspended 
in  the  cylinder,  and  an  inverted  conical  condenser  which  serves 
as  a  top. 


112  HOT    EXTRACTION 

The  aggregate  is  prepared  for  analysis  by  heating  it  in  a 
tin  dish  on  the  hot  plate  until  it  is  sufficiently  soft  to  be  dis- 
integrated by  means  of  a  large  spoon.  The  disintegrated  aggre- 
gate is  then  allowed  to  cool.  Five  hundred  grams  of  aggregates 
containing  particles  larger  than  ^  inch  in  diameter  and  three 
hundred  grams  of  aggregates  with  all  particles  smaller  than 
%  inch  are  then  closely  packed  in  the  wire  basket  and  covered 
with  a  disk  or  wad  of  absorbent  cotton  or  felt.  From  175  to 
200  cubic  centimeters  of  carbon  disulphide  are  next  placed  in  the 
inside  vessel,  in  which  the  wire  basket  should  be  suspended. 
The  top  is  then  placed  in  position  and  cooling  water  circulated 
through  it.  Heat  is  applied  by  means  of  the  electric-light  bulb. 
The  solvent  is  boiled  in  the  lower  part  of  the  extractor,  and 
condenses  on  the  under  surface  of  the  top,  from  which  it  drips 
upon  the  wad  of  absorbent  cotton  and  then  percolates  through 
the  sample.  A  complete  extraction  may  be  made  in  three 
hours.  At  the  end  of  this  time  the  apparatus  is  allowed  to 
cool  and  the  basket  containing  the  extracted  aggregate  care- 
fully removed.  After  thoroughly  drying  the  aggregate  is  placed 
upon  a  pan  of  the  rough  balance  and  weighed.  The  difference 
between  this  weight  and  the  original  weight  taken  shows  the 
amount  of  bitumen  extracted  which  is  calculated  upon  a  per- 
centage basis  of  the  original.  This  figure  should  be  corrected 
for  fine  mineral  matter  which  passes  through  the  meshes  of  the 
wire  basket  as  follows:  The  solution  of  extracted  bitumen  is 
thoroughly  agitated  and  measured  in  a  glass  graduate.  Five 
or  ten  cubic  centimeters  are  then  poured  into  a  weighed  plati- 
num crucible  or  dish,  burned,  and  ignited  to  ash.  The  amount 
of  mineral  matter  in  the  entire  solution  may  then  be  calculated 
from  the  amount  of  ash  produced  from  that  portion  ignited. 
The  total  percentage  of  such  ash  is  then  deducted  from  the  per- 
centage of  bitumen  already  calculated  in  order  to  obtain  the 
true  percentage  of  bitumen.  The  amount  of  this  correction 
will  ordinarily  vary  from  o.i  per  cent  in  uniformly  coarse  ag- 
gregates to  i.o  or  2.0  per  cent  in  the  analysis  of  aggregates 
containing  a  considerable  amount  of  very  fine  mineral 
matter. 


RECOVERY    OF    BITUMEN 


113 


RECOVERY   OF   BITUMEN 

If  an  extraction  has  been  made  upon  a  sufficiently  large 
sample  of  bituminous  aggregate  to  yield  from  30  to  50  grams 
of  pure  bitumen,  it  may  be  desirable  to  recover  and  examine 
the  bitumen.  When  this  is  so  the  apparatus  shown  in  Fig. 
38  will  be  found  convenient  and  fairly  safe  for  the  distillation 
and  recovery  of  such  inflammable  solvents  as  carbon  disulphide. 
In  the  laboratory  of  the  Office  of  Public  Roads  and  Rural  Engi- 
neering this  apparatus  is  arranged  so  that  the  glass  tubing 
passes  through  a  stone  partition  between  two  sections  of  a  small 


FIG.  38.     Distillation  Apparatus  for  Recovering  Bitumen 

hood,  thus  keeping  the  distilling  and  receiving  apparatus  entirely 
separated. 

The  solution  of  bitumen  should  be  allowed  to  stand  over- 
night in  order  to  permit  the  settling  of  any  fine  mineral  matter 
that  is  sometimes  carried  through  the  extractor.  The  solution  is 
then  decanted  into  the  flask  a,  and  the  solvent  is  driven  off 
by  means  of  heat  from  an  incandescent  lamp  until  the  residue 
is  of  a  thick,  sirupy  consistency.  Meanwhile  the  solvent  is 
condensed  and  recovered  in  the  flask  b.  The  residue  is  poured 
into  an  n -centimeter  porcelain  evaporating  dish  and  evapor- 
ated on  a  steam  bath.  The  most  scrupulous  care  must  be  taken 


114  FILTRATION    EXTRACTION 

at  all  times  that  no  flames  are  in  its  immediate  vicinity.  Evap- 
oration is  carried  on  at  a  gentle  heat,  with  continual  stirring, 
until  foaming  practically  ceases.  It  is  advisable  to  have  a 
large  watch  glass  at  hand  to  smother  the  flames  quickly  should 
the  material  ignite.  As  the  foaming  subsides,  the  heat  of  the 
steam  bath  may  be  gradually  raised,  and  evaporation  is  con- 
tinued until  the  bubbles  beaten  or  stirred  to  the  surface  of  the 
bitumen  fail  to  give  a  blue  flame  or  odor  of  sulphur  dioxide 
when  ignited  by  a  small  gas  jet.  The  dish  of  bitumen  should 
then  be  set  in  a  hot-air  oven  maintained  at  105°  C.  for  about 
an  hour,  after  which  it  is  allowed  to  cool.  Its  general  char- 
acter is  noted  and  any  tests  for  bitumens  that  are  necessary 
are  then  made  upon  it. 


FILTRATION  EXTRACTION 
Equipment: 

short  stem  funnel,  2^2  inches  in  diameter. 
9-centimeter  Schleicher  &  Schull  597  filter  paper. 
2^2 -inch  watch  glass. 
3  250  cubic  centimeter  Erlenmeyer  flasks. 
piece  glazed  paper  about  12  inches  square, 
small  camel's-hair  brush, 
small  platinum  dish, 
wash  bottle  for  solvent, 
hot-air  oven. 

Bunsen  burner  and  tubing, 
spatula. 

nichrome  triangle, 
small  metal  pan. 
analytical  balance,  capacity  100  grams,  sensitive  to  O.I  milligram. 

Method. — When  it  is  not  desired  to  recover  the  bitumen  in  a  bituminous 
aggregate  containing  no  mineral  particles  coarser  than  sand,  and  a  small 
centrifugal  extractor  is  not  at  hand,  the  following  method,  substantially  as 
described  by  Richardson,*  will  be  found  useful. 

The  bituminous  aggregate  is  first  disintegrated  by  warming  it  in  a  small 
metal  pan  and  then  allowed  to  cool.  A  ten-gram  sample  is  then  weighed  out 
upon  a  watch  glass  and  carefully  transferred  to  a  Schleicher  &  Schull  597 
filter  paper  folded  in  the  funnel.  The  funnel  is  then  placed  in  the  mouth  of  a 
250-cc.  Erlenmeyer  flask.  A  fine  stream  of  carbon  disulphide  is  directed  on 
the  surface  of  the  aggregate  until  it  is  thoroughly  saturated,  but  no  excess  of 
solvent  is  used.  The  moistened  aggregate  is  then  allowed  to  stand  until  it  has 
softened  and  settled  upon  the  filter.  The  filter  is  then  filled  with  carbon 
disulphide  to  within  an  eighth  of  an  inch  of  the  top  and  the  funnel  covered  with 
a  2K -inch  watch  glass.  As  percolation  proceeds,  additional  solvent  is  added, 
and  filtration  may  be  hastened  by  occasionally  washing  between  the  paper 
and  funnel  with  the  solvent.  During  the  day  the  aggregate  is  washed  as  clean 
as  possible,  and  both  it  and  the  filtrate  are  allowed  to  stand  overnight. 

*  "  The  Modern  Asphalt  Pavement."    John  Wiley  &  Sons,  p.  571. 


GRADING    OF    MINERAL    AGGREGATES  115 

The  next  morning  the  funnel  is  placed  in  a  clean,  dry  flask,  and  the  filtrate 
is  carefully  decanted  into  another  flask  without  disturbing  the  sediment.  A 
small  portion  of  carbon  disulphide  is  then  poured  into  the  first  flask,  shaken 
up,  and  poured  upon  the  filter.  Any  remaining  sediment  is  then  washed  from 
the  flask  upon  the  filter,  a  feather  being  used  if  necessary  to  thoroughly  clean 
it.  The  mineral  aggregate  upon  the  filter  is  then  washed  until  the  filtrate 
runs  colorless. 

After  thoroughly  drying  in  air,  the  funnel  and  contents  are  placed  in  an 
oven  at  105°  C.  for  30  minutes,  after  which  it  is  separated  from  the  filter  over  a 
piece  of  glazed  paper  by  scraping  with  a  blunt  spatula  and  rubbing  between 
the  fingers,  care  being  taken  not  to  detach  any  fibers  of  the  paper.  It  is  then 
dusted  into  a  tared  watch  glass  and  weighed. 

Meanwhile  the  filtrate  is  poured  into  a  weighed  platinum  dish  and  burned 
under  a  well-ventilated  hood.  If  the  dish  is  not  sufficiently  large  to  hold  all 
at  one  time,  it  is  burned  in  portions,  but  care  must  be  taken  that  the  dish  and 
contents  are  thoroughly  cool  before  adding  a.  fresh  portion.  The  dish  is 
finally  ignited  and  the  filter  paper  placed  in  it  and  also  ignited.  It  is  then 
cooled  and  weighed.  The  combined  weight  of  the  contents  of  the  watch  glass 
and  the  platinum  dish  is  then  taken  as  the  weight  of  mineral  matter  and  the 
weight  of  bitumen  ascertained  by  subtracting  the  combined  weight  from 
that  of  the  original  sample.  The  percentages  of  aggregate  and  bitumen  are 
calculated  upon  a  percentage  basis  of  the  whole.  The  recovered  aggregate 
may  then  be  subjected  to  a  sieve  analysis. 


GRADING  OF  MINERAL  AGGREGATES 

Equipment: 

i  set  of  8-inch  stone  sieves  with  circular  openings  of  1%, 

1^4 j  i,  ^4,  y£j  and  %  inches,  respectively, 
i  set  of  8-inch  brass  sand  sieves  of  10,  20,  30,  40,  50,  80, 

100,  and  200  mesh,  respectively,  with  pan  and  cover, 
i  rough  balance,  capacity   i   kilogram,  sensitive  to   o.i 

gram. 

i  i^-inch  stiff,  flat  brush. 
Several  sheets  of  manila  paper. 

Method. — It  is  often  desirable  to  make  a  mechanical  analy- 
sis not  only  of  an  extracted  aggregate  but  also  of  a  mineral 
aggregate  which  is  to  be  used  in  a  bituminous  mix.  In  the 
latter  case  almost  any  reasonable-size  sample  may  be  secured, 
but  with  extracted  aggregates  the  size  of  the  sample  is  limited 
by  the  amount  of  bituminous  aggregate  which  it  is  practicable 
to  obtain  in  a  single  extraction.  In  such  cases  it  is  customary 
to  work  with  the  entire  mass  of  extracted  aggregate  and  to 
consider  all  mineral  matter  obtained  as  a  correction,  by  burning 
and  igniting  the  nitrate,  as  material  passing  a  2oo-mesh  sieve. 
Results  may  then  be  expressed  on  a  percentage  basis  of  the 


116  GRADING    OF    MINERAL    AGGREGATES 

original  bituminous  aggregate  or  upon  the  extracted  aggregate 
as  occasion  may  require.  In  reporting  results  the  percentage 
of  fine  material  is  sometimes  given  first,  each  larger  size  fol- 
lowing in  order,  while  in  other  cases  the  opposite  procedure 
is  followed  and  the  coarsest  size  reported  first. 

For  aggregates  containing  particles  too  large  to  pass  a  10- 
mesh  screen,  the  stone  sieves  are  used,  and  are  stacked  in  their 
regular  order  over  a  sheet  of  heavy  paper,  with  the  largest 
size  required  on  top.  The  weighed  amount  of  stone  is  placed 
on  the  largest  sieve  and  is  carefully  protected  from  drafts  which 
might  carry  away  any  of  the  fine  material.  The  upper  sieve 
is  then  removed  from  the  stack  and  shaken  over  a  large  sheet 
of  paper  until  no  more  particles  come  through.  The  material 
thus  retained,  including  any  fragments  caught  in  the  meshes 
of  the  sieve,  is  weighed  and  that  which  passes  is  added  to  the 
contents  of  the  succeeding  sieve.  This  operation  is  repeated  with 
each  succeeding  siev^. 

When  grading  sands  or  fine  aggregates,  it  is  customary  to 
take  a  ico-gram  sample  in  order  that  the  weights  may  give 
direct  percentages  to  tenths  of  one  per  cent.  The  sieves  are 
stacked  in  regular  order,  with  the  2oo-mesh  sieve  resting  on 
the  pan.  The  sample  is  brushed  on  the  top  sieve,  after  which 
the  cover  is  put.  on  and  the  stack  agitated  for  about  five  min- 
utes with  both  rocking  and  circular  shaking.  Each  sieve  is 
removed  in  order,  and  shaken  and  tapped  on  a  clean  piece  of 
paper  until  no  appreciable  amount  of  material  comes  through. 
All  lumps  are  broken  up  by  crushing  them  against  the  side  of 
the  sieve  with  the  finger  or  a  small  spatula.  The  contents 
of  the  sieve  are  emptied  into  the  pan  of  the  balance.  All  par- 
ticles caught  in  the  mesh  are  removed  by  brushing  across  the 
under  side  of  the  sieve  and  are  added  to  the  contents  of  the 
pan.  As  great  opportunity  exists  for  wide  variations  in  the 
results  of  sand  gradings  made  by  different  persons,  owing  to 
the  possibility  of  always  getting  a  little  more  material  to  pass 
by  continued  shaking,  it  is  well  for  the  novice  to  repeat  his 
sifting  on  any  given  mesh,  after  having  weighed  it,  in  order 
to  see  what  further  loss  he  can  produce.  If  his  judgment  has 


PROPOSED    REVISED    STANDARD    METHOD 


117 


not  erred,  several  minutes'  further  sifting  should  not  produce 
a  loss  of  over  0.5  gram. 

Where  coarse  aggregates  have  considerable  material  passing 
a  lo-mesh  sieve  and  it  is  desired  to  grade  this  material  further 
it  should  be  weighed  and  well  mixed,  quartered,  if  necessary, 
and  a  ico-gram  sample  should  be  passed  through  the  sand 
sieves.  From  the  percentages  so  obtained  and  the  weight  of 
material  passing  the  lo-mesh  sieve,  the  percentages  of  the 
total  aggregate  which  these  finer  materials  represent  may  be 
calculated. 

In  the  above  operations,  screens  and  sieves  recommended  in 
1916  by  Committee  D-4  of  The  American  Society  for  Testing 
Materials  should  be  used.  Following  are  given  methods  for 
making  a  mechanical  analysis  of  three  types  of  mineral  aggre- 
gate as  recommended  in  1916  by  the  Committee: 


Proposed  Revised  Standard  Method 

for 

Making  a  Mechanical  Analysis  of  Sand  or  Other  Fine  Highway 
Material ,  Except  for  Fine  Aggregate  Used  in  Cement  Concrete 

,  The  method  shall  consist  of  (i)  drying  at  not  over  110°  C.  (230°  F.)  to  a 
constant  weight  a  sample  weighing  50  g. ;  (2)  passing  the  sample  through  each 
of  the  following  mesh  sieves  (American  Society  for  Testing  Materials  standard 
sieves)  :* 


DIAMETER 

OF  WIRE 

In. 

Mm. 

10   

o  027 

o  6858 

20  

O.OI65 

O.4.IQI 

V)  .  . 

o.oi^ys 

O  .  ^-IQ2  ^ 

4.O 

o  01025 

O  26o^S 

so 

o  ooo 

o  22865 

80       

O  OOS7S 

o  1460 

TOO  

O.OO4S 

0.1147 

2OO  ... 

O.OO2T,*, 

O.OSQ6Q 

*  The  order  in  which  the  sieves  are  to  be  used  in  the  process  of  sifting  is  immaterial  and  may 
be  left  optional;  but  in  reporting  results  the  order  in  which  the  sieves  have  been  used  shall  be 
stated. 


118  PROPOSED    STANDARD    METHOD 

(3)  determining  the  percentage  by  weight  retained  on  each  sieve,  the  sifting 
being  continued  on  each  sieve  until  less  than  I  per  cent  of  the  weight  retained 
on  each  sieve  shall  pass  through  the  sieve  during  the  last  minute  of  sifting,  and 

(4)  recording  the  mechanical  analysis  in  the  following  manner: 

Passing  2OO-mesh  sieve ; =  per  cent 

Passing  loo-mesh  sieve  and  retained  on  a  2OO-mesh  sieve  =  

Passing    8o-mesh  sieve  and  retained  on  a  loo-mesh  sieve  =  

Passing    5o-mesh  sieve  and  retained  on  an  8o-mesh  sieve  =  


100.00 

Proposed  Standard  Method 

for 

Making  a  Mechanical  Analysis  of  Broken  Stone  or  Broken  Slag, 
Except  for  Aggregates  Used  in  Cement  Concrete 

The  method  shall  consist  of  (i)  drying  at  not  over  110°  C.  (230°  F.)  to 
a  constant  weight  a  sample  weighing  in  pounds  six  times  the  diameter  in 
inches  of  the  largest  holes  required;  (2)  passing  the  sample  through  such  of  the 
following  size  screens  having  circular  openings  as  are  required  or  called  for  by 
the  specifications,  screens  to  be  used  in  the  order  named:  8.89  cm.  (3^2  in.), 
7.62  cm.  (3  in.),  6.35  cm.  (2^  in.),  5.08  cm.  (2  in.),  3.81  cm.  (i#  in.),  3.18  cm. 
(iX  in.),  2.54  cm.  (i  in.),  1.90  cm.  (^  m.),^i.27  cm.  (^  in.),  and  0.64  cm. 
(%  in.)  ;  (3)  determining  the  percentage  by  weight  retained  on  each  screen,  and 
(4)  recording  the  mechanical  'analysis  in  the  following  manner: 

Passing  o.64-cm.  (>^-in.)  screen  ......................    =     .....  per  cent 

Passing  i.27-cm.  (J^-in.)  screen  and  retained  on  a  0.64- 

cm.  (  j<4-inch)  screen  ..........  ....................    =     ..... 

Passing  i.9O-cm.  (^-in.)  screen  and  retained  on  a  1.27- 

cm.  (>£-in.)  screen  ................  .  ...............    =     ..... 

Passing  2.54-cm.  (i-in.)  screen  and  retained  on  a  i.  go-cm. 

(K-in.)  screen  ...................................    =     ..... 


100.00 


Proposed  Standard'  Method 

for 

Making  a  Mechanical  Analysis  of  Mixtures  of  Sand  or  Other  Fine 

Material  with  Broken  Stone  or  Broken  Slag,  Except  for 

Aggregates  Used  in  Cement  Concrete 

The  method  shall  consist  of  (i)  drying  at  not  over  no°C.  (230°  F.)  to  a. 
constant  weight  a  sample  weighing  in  pounds  six  times  the  diameter  in  inches 
of  the  largest  holes  required;  (2)  separating  the  sample  by  the  use  of  a  screen 
having  circular  openings  0.64  cm.  (J4  in.)  in  diameter;  (3)  examining  the  por- 
tion retained  on  the  screen  in  accordance  with  the  proposed  Standard  Method 
for  Making  a  Mechanical  Analysis  of  Broken  Stone  or  Broken  Slag,  Except  for 
Aggregates  Used  in  Cement  Concrete;  (4)  examining  the  portion  passing  this 
screen  in  accordance  with  the  proposed  Standard  Method  for  Making  a 
Mechanical  Analysis  of  Sand  or  Other  Fine  Highway  Material,  Except  for 
Fine  Aggregate  Used  in  Cement  Concrete,  and  (5)  recording  the  mechanical 
analysis  in  the  following  manner: 


VALUE    OF    TESTS    FOR    BITUMINOUS    AGGREGATES         119 

Passing  2OO-mesh  sieve =     per  cent 

Passing  loo-mesh  sieve  and  retained  on  a  2oo-mesh  sieve  =     

Passing    8o-mesh  sieve  and  retained  on  a  loo-mesh  sieve  =     

Passing  lo-mesh  sieve  and  retained  on  a  2O-mesh  sieve..  =     " 

Passing  o.64-cm.  (,J4-in.)  screen  and  retained  on  a  lo-mesh 

sieve =     

Passing  i.2y-cm.  (X-in.)  screen  and  retained  on  a  o.64-cm. 

(X-in.)  screen =     

Passing  I. go-cm.  (24-in.)  screen  and  retained  on  a  i.27-cm. 

(K-in.)  screen  .  ,  .  = 


100. OO 
VALUE   OF   TESTS   FOR   BITUMINOUS   AGGREGATES 

The  determination  of  bitumen  in  bituminous  aggregate  is 
particularly  valuable  as  a  laboratory  control  test  for  the  plant 
or  factory  manufacture  of  such  aggregates.  The  serviceability 
of  a  bituminous  aggregate  is  not  only  dependent  upon  the 
physical  and  chemical  properties  of  the  bituminous  cement,  but 
also  upon  the  percentage  of  such  cement  which  is  present. 
Too  much  may  be  almost  as  bad  as  too  little,  and  the  exact 
percentage  should  therefore  be  adjusted  to  meet  the  character 
and  grading  of  the  mineral  aggregate  which  is  used.  When 
once  the  proper  combination  of  bituminous  cement  and  a  given 
aggregate  has  been  experimentally  ascertained,  the  per  cent  of 
bitumen  as  determined  by  test  should,  for  different  lots  of  the 
same  bituminous  aggregate,  fall  within  comparatively  narrow 
limits. 

While  in  the  determination  of  total  bitumen  or  those  mate- 
rials consisting  mainly  of  bitumen  it  is  highly  desirable  that 
for  the  sake  of  uniformity  all  determinations  be  made  with  the 
cold  solvent,  the  same  is  not  so  important  in  the  case  of  bitu- 
minous aggregates.  Hot  and  cold  methods  of  extraction  are, 
therefore,  equally  serviceable  for  the  latter,  and  the  results 
obtained  by  both  methods  are  ordinarily  quite  comparable  and 
to  all  extents  and  purposes  equivalent.  It  is  well  known  that 
many  bituminous  materials  are  more  soluble  in  a  hot  solvent 
than  in  the  same  solvent  cold.  The  actual  difference  is  neces- 
sarily greater  in  materials  rich  in  bitumen  than  for  those  com- 
paratively poor  in  the  same  bitumen.  Thus  a  given  type  of 


120        VALUE    OF    TESTS    FOR    BITUMINOUS    AGGREGATES 

relatively  pure  bitumen  may,  for  the  sake  of  illustration,  be 
considered  as  being  as  much  as  2  per  cent  more  soluble  in  a  hot 
solvent  than  in  the  same  solvent  cold.  If  this  same  bitumen 
were,  however,  mixed  with  nine  times  its  weight  of  mineral 
matter,  it  will  be  seen  that  the  difference  in  the  actual  per- 
centage of  bitumen  determined  by  hot  and  cold  extractions 
will  amount  to  not  over  0.2  per  cent. 

In  the  extraction  of  bituminous  aggregates  it  is  frequently  de- 
sirable to  recover  and  examine  both  the  extracted  bitumen  and 
the  mineral  aggregate.  The  bitumen  may  thus  often  be  iden- 
tified and  its  suitability  as  a  cementing  medium  ascertained. 
The  mechanical  grading  of  the  aggregate  will  also  indicate  the 
suitability  of  the  mixture  for  a  specific  purpose,  provided  the 
characteristics  of  the  Bituminous  cement  are  known.  If  the 
specific  gravity  of  both  bitumen  and  mineral  matter  are  deter- 
mined as  well  as  the  relative  proportions  in  which  each  occur, 
it  will  be  possible  to  ascertain  the  rational  per  cent  of  bitumen 
in  the  mixture  and  also  its  theoretical  maximum  density  as 
described  under  "Bituminous  Aggregates,"  in  Part  III. 


NOTES 


PART    m.    CHARACTERISTICS    OF    THE    MORE 
IMPORTANT  BITUMINOUS  MATERIALS 

FLUID  PETROLEUM  PRODUCTS  AND  EMULSIONS 

Fluid  petroleum  products  are  used  as  dust  preventives,  fluxes, 
carpeting  mediums,  and  occasionally,  when  very  viscous,  as  bitu- 
minous cements  for  certain  types  of  mineral  aggregates.  Emul- 
sifying oils  and  petroleum  emulsions  are  used  as  dust  preventives 
or  light  carpeting  mediums,  while  asphalt  emulsions  are  some- 
times used  as  bituminous  cements. 

Almost  any  sufficiently  fluid  petroleum  product  may  be  used 
as  a  dust  preventive  and,  unless  successive  applications  are  ex- 
pected to  build  up  a  bituminous  carpet,  no  tests  other  than 
viscosity  and  relatively  low  loss  by  volatilization  are  important. 
If,  however,  the  material  is  to  serve  as  a  carpeting  medium,  other 
tests  are  of  value,  and  as  a  rule  all  of  the  fluid  petroleum 
products  may  ordinarily  be  subjected  to  the  following  tests  to 
advantage: 

ORDINARY   TESTS 

1.  Specific  Gravity  25725°  C. 

2.  Specific  Viscosity,  Engler,  50  c.c. 

a.  Preferably  at  25°  C.  if  the  material  is  to  be  used  cold. 

b.  At  50°  C.  or  100°  C.  if  the  material  is  to  be  used  hot. 

3.  Float  Test  at  50°  C.  if  the  material  is  to  be  used  primarily 

as  a  carpeting  medium  or  a  bituminous  cement. 

4.  Flash  Point  °  C. 

a.  Open-cup  method  for  non-volatile  products. 

b.  Closed-cup  method  for  volatile,  crude,  topped  or  cut- 

back products,  particularly  if  they  are  to  be  applied 
hot. 

121 


122      INTERPRETATION  OF  RESULTS  IN  TABLE  I 

5.  Volatilization  Test,  50  grams,  5  hours. 

a.  At  100°  C.  for  cut-back  products  which  are  required 

to  harden  rapidly  after  use. 

b.  At  163°  C.  for  practically  all  products. 

6.  Consistency  of  Residue  from  Volatilization  Test  for  carpet- 

ing mediums  and  bituminous  cements. 

a.  Float  Test  at  50°  C.  if  too  soft  for  penetration  test. 

b.  Penetration  Test  25°  C.,  100  grams,  5  seconds,  when 

possible. 

7.  Total  Bitumen. 

Organic  Matter  Insoluble  in  Carbon  Bisulphide. 
Inorganic  Matter  Insoluble  in  Carbon  Bisulphide. 

8.  Asphaltenes. 

9.  Carbenes  on  cut-back  products. 
10.  Fixed  carbon  when  possible. 

INTERPRETATION  OF  RESULTS  IN  TABLE  I 

Table  I,  on  page  123,  shows  the  results  of  the  above  tests 
upon  typical  fluid  petroleum  products  of  interest  in  highway 
engineering. 

The  heavy  distillate  indicated  by  its  fairly  high  specific 
gravity  should  be  considered  merely  as  a  dust  preventive.  This 
product  is  very  fluid,  as  shown  by  its  low  specific  viscosity  at 
25°  C.,  and  is  therefore  susceptible  to  application  by  means  of 
an  ordinary  gravity  water  sprinkler.  Its  flash  point  is  rela- 
tively high  for  a  distillate,  and  this,  together  with  a  loss  at 
163°  C.,  of  only  12.6  per  cent,  indicates  that  it  would  not  vola- 
tilize too  rapidly  after  application.  The  fact  that  the  residue 
from  the  volatilization  test  is  fluid  shows  that  it  will  develop 
no  appreciable  binding  value  after  application,  and  this,  together 
with  a  total  absence  of  asphaltenes  and  practically  no  fixed 
carbon,  shows  it  to  be  a  permanent  lubricant  which  should  be 
used  sparingly  so  as  not  to  disintegrate  the  road  surface.  Being 
a  bituminous  distillate,  it  is  naturally  entirely  soluble  in  carbon 
disulphide. 

The  medium  crude  petroleum  is  of  Mexican  origin,  its  gravity 
being  considerably  lower  than  the  maltha.  Its  viscosity  at 


NOTES 


NOTES 


ANALYSES    OF    FLUID    PETROLEUM    PRODUCTS 


123 


a* 

f! 

§ 


Mediu 
Crud 


Heavy 
Distillate 


•  O  10 

.co  -5 


u 


CO  O  >O 


.  w 

•-.Co 


O  O 


8  N   OOO 

8d  d  t^ 
c* 


r,  « 


ion 


ri- 
O\00  C< 

d  Tt-od 

OM-I 


. 

\O  HH 


8  N 


ONO 


OvO 


-ON 


O  O  O  N 

g  ci  d  to 


O  >O»O 

O>  O   O 


82" 


is  :8"88 


dr-"-O 


<J6? 


o-  o  o 
u  6  6 


:  x 


Asp 


naph 


S          PQ 


^jg-^ggg 


e 


Bit.  insol. 
Carbenes 
Fixed  Carbo 


124       INTERPRETATION  OF  RESULTS  IN  TABLE  I 

25°  C.  shows  it  to  be  fairly  fluid  and  susceptible  to  cold  appli- 
cation, although  at  as  high  as  50°  C.  it  is  more  viscous  than 
the  distillate.  Its  very  low  flash  point  and  high  loss  at  163°  C. 
shows  it  to  contain  a  large  amount  of  volatile  products.  The 
fact  that  a  float  test  of  i'  23"  is  obtained  at  50°  C.  upon  the 
residue,  indicates  a  tendency  to  harden  to  a  point  at  which 
it  may  serve  as  a  weak  binding  medium.  Its  asphaltic  nature 
is  indicated  by  its  relatively  high  percentages  of  asphaltenes 
and  fixed  carbon.  Like  the  other  products  it  is  practically  pure 
bitumen,  being  almost  completely  soluble  in  carbon  disulphide. 
Such  a  material  may  be  considered  as  other  than  a  mere  dust 
preventive,  as  it  may  be  used  to  build  up  a  very  thin  bituminous 
carpet.  Unless  used  sparingly,  however,  because  of  the  fact 
that  it  hardens  very  slowly,  it  will  tend  to  emulsify  on  the 
road  surface  in  wet  weather  and  produce  a  disagreeable  mud. 
The  three  residual  petroleums  may  be  considered  together. 
It  will  be  noted  that  the  viscosity  of  all  are  too  high  to  permit 
of  their  application  to  a  road  surface  without  first  heating 
them  to  a  state  of  considerably  greater  fluidity.  Their  rela- 
tively high  flash  point  and  low  loss  by  volatilization  at  163°  C. 
show  them  to  be  residuals  and  not  crude  products.  They  are 
all  practically  completely  and  equally  soluble  in  carbon  disul- 
phide and  carbon  tetrachloride,  which  shows  that  they  have 
not  been  injuriously  cracked  in  their  manufacture.  The  residue 
from  the  volatilization  test  of  the  paraffin  residuum  is  too  fluid 
for  a  float  test  at  50°  C.,  which,  together  with  the  very  low 
percentage  of  asphaltenes  and  fixed  carbon,  shows  the  material 
to  be  absolutely  unsuited  for  use  as  a  carpeting  medium.  As  it 
is  too  viscous  to  apply  cold  it  would  also  be  an  unsuitable  dust 
preventive.  The  semi-asphaltic  residuum  which  is  a  Texas 
product  is  sufficiently  viscous  to  show  an  appreciable  float  test 
at  50°  C.,  but  is  incapable  of  hardening  materially  as  shown 
by  its  almost  negligible  loss  at  163°  C.  and  the  very  slight 
increase  in  float  test  of  the  residue  as  compared  with  the  orig- 
inal material.  While  in  consistency  and  percentage  of  asphal- 
tenes and  fixed  carbon  it  is  superior  to  the  paraffin  residuum, 
it  would  nevertheless  make  an  unsatisfactory  carpeting  medium. 


NOTES 


NOTES 


INTERPRETATION    OF    RESULTS   IN    TABLE    I  125 

The  asphaltic  residuum  is  from  a  California  petroleum  and, 
while  greatly  superior  to  the  other  two  as  a  carpeting  medium, 
would  prove  far  from  ideal  unless  used  very  sparingly  so  that 
the  carpet  would  be  very  thin.  It  is  quite  viscous,  as  shown 
by  its  specific  viscosity  at  100°  C.  and  its  float  test  at  50°  C. 
It  also  hardens  up  to  some  extent  under  the  volatilization  test, 
producing  a  residue  of  about  the  same  consistency  as  that  of 
the  medium  crude  asphaltic  petroleum.  It  is,  however,  prefer- 
able to  the  latter  for  use  as  a  carpeting  medium  as  in  its  original 
condition  it  represents  a  more  advanced  stage  of  hardening  and 
of  cementitiousness,  and  will  not  so  readily  emulsify  with  water 
and  produce  an  oily  mud  on  the  road  surface.  A  fairly  thick 
bituminous  carpet  constructed  with  such  a  product  is,  how- 
ever, more  than  apt  to  shove  under  traffic,  owing  to  its  mechan- 
ical instability,  indicated  by  its  relatively  low  percentages  of 
asphaltenes  and  fixed  carbon. 

While  none  of  the  petroleum  residuums  have  much  to  rec- 
ommend them  for  direct  use  in  road  treatment  or  construction 
under  ordinary  conditions,  they  might  all  be  satisfactorily  used 
as  fluxes  for  the  harder  asphalts  in  producing  asphalt  cements 
of  various  consistencies.  They  conform  in  characteristics  to 
the  three  types  of  fluxes  usually  recognized  as  paraffin,  semi- 
asphaltic  and  asphaltic.  Fluxes  produced  from  paraffin  petro- 
leums usually  have  a  specific  gravity  of  from  0.920  to  0.940. 
The  semi-asphaltic  fluxes  lie  between  0.940  and  0.975,  while  the 
asphaltic  fluxes  run  from  0.975  to  i.oio  and  over.  In  general, 
as  fluxes  increase  in  specific  gravity  they  must  be  used  in 
greater  quantity  with  a  given  refined  asphalt  to  produce  an 
asphalt  cement  of  given  penetration.  Their  flash  point  should 
be  above  163°  C.  as  this  is  the  temperature  to  which  they  are 
likely  to  be  heated  when  being  combined  with  the  solid  asphalts. 
They  should  not  lose  over  5%  by  weight  when  subjected  to 
the  volatilization  test  for  5  hours  at  163°  C.  The  residues 
from  this  test  may  or  may  not  harden  appreciably,  but  the 
degree  of  hardening  should  never  cause  the  asphalt  cement 
in  which  they  are  incorporated  to  show  a  loss  of  over  50%  in 
penetration  when  subjected  to  the  volatilization  test  at  163°  C. 


126       INTERPRETATION  OF  RESULTS  IN  TABLE  I 

Fluxes. will  be  again  considered  in  connection  with  asphalts  and 
asphalt  cements. 

The  maltha  is  of  California  origin  and  possesses  certain 
characteristics  of  a  cut-back  asphalt.  Although  a  crude  prod- 
uct, it  is  very  viscous,  as  shown  by  its  viscosity  at  100°  C., 
and  is  susceptible  only  to  hot  application.  Considerable  care 
should  be  exercised  in  heating  it,  owing  to  its  low  flash  point. 
It  shows  a  relatively  high  loss  at  163°  C.  The  fact  that  the 
residue  gives  a  high  float  test  at  50°  C.  and  that  it  is  truly  an 
asphalt  cement,  as  indicated  by  its  penetration,  shows  an 
absence  of  non- volatile  oils.  The  material  is  therefore  similar 
to  a  soft  asphalt  cement  cut-back  with  light  volatile  oils.  As  a 
carpeting  medium  it  is  greatly  superior  to  any  other  product 
in  the  table  so  far  considered.  After  application  it  should 
rapidly  harden  to  a  point  where  with  a  dressing  of  stone  chips 
it  would  form  a  relatively  stable  carpet  which  should  not  shove 
under  traffic  if  it  were  not  over  one-half  inch  in  thickness. 
Its  high  percentage  of  asphaltenes  and  relatively  high  percent- 
age of  fixed  carbon  for  a  crude  fluid  product  indicate  its  highly 
asphaltic  nature.  If  topped  it  would  in  many  respects  resemble 
the  cut-back  asphalt  shown  in  the  last  column. 

The  cut-back  asphalt  is  almost  a  semisolid,  as  shown  by  its 
float  test  at  50°  C.  It  has  a  higher  specific  gravity  than  any 
of  the  other  products.  While  its  flash  point  is  relatively  high 
and  its  loss  at  163°  C.  small,  the  residue  is  a  relatively  hard 
asphalt  cement  having  a  penetration  of  98.  Its  high  percent- 
age of  asphaltenes  and  fixed  carbon  indicates  its  asphaltic 
nature.  This  material  might  make  an  even  better  carpeting 
medium  than  the  maltha  were  it  not  for  the  fact  that  it  is 
so  nearly  semisolid  that  great  difficulty  would  be  experienced 
in  getting  it  to  stick  to  an  ordinary  road  surface  even  if  first 
heated  to  a  very  fluid  state.  It  is,  however,  admirably  suited 
to  the  surface  treatment  of  a  bituminous  macadam  or  bitu- 
minous concrete  surface  to  replace  an  old  seal  coat  after  it 
has  practically  worn  away.  Such  materials  have  been  used  to 
some  extent  in  the  construction  of  bituminous  concrete  roads. 
When  heated  they  possess  the  advantage  of  being  able  to  mix 


NOTES 


NOTES 


INTERPRETATION    OF    RESULTS    IN    TABLE    II  127 

with,  and  thoroughly  coat  coarse  mineral  aggregates,  but  until 
they  have  lost  the  light  oils  used  in  cutting-back  the  asphalt 
cement  they  do  not  possess  sufficient  mechanical  stability  to 
hold  the  aggregate  in  place  under  heavy  traffic.  When  not 
exposed  to  surface  conditions  they  do  not  lose  their  volatiles 
for  a  very  long  time  and  the  road  is  therefore  apt  to  shove 
and  wave  under  traffic. 


INTERPRETATION  OF  RESULTS  IN  TABLE  II 

In  Table  II,  on  page  128,  are  given  the  characteristics  of 
certain  emulsifying  oils  and  emulsions.  No  general  scheme  of 
examination  in  common  use  is  given  for  these  products  as  they 
are  not  so  widely  used  as  the  other  fluid  products,  and  the 
exact  method  of  examination  should  depend  upon  their  pros- 
pective use  and  just  what  characteristics  are  developed  as  the 
analyst  proceeds  in  his  examination. 

The  emulsifying  oil  consists  mainly  of  what  is  known  as 
an  alkaline  sludge  obtained  by  refining  certain  petroleum  dis- 
tillates with  caustic  soda.  While  it  does  not  contain  water, 
it  may  be  mixed  or  diluted  with  water  to  almost  any  desired 
degree  of  fluidity  and  therefore  readily  applied  at  any  desired 
rate  to  a  road  surface.  The  character  of  the  residue  from 
the  volatilization  test  and  the  low  percentage  of  asphaltenes 
and  fixed  carbon  show  it  'to  be  unsuitable  for  any  use  other 
than  as  a  dust  preventive. 

The  residual  emulsion  contains  a  large  amount  of  water, 
which  is  mostly  driven  off  in  the  volatilization  test  at  105°  C., 
leaving  a  viscous,  sticky  petroleum  residue,  together  with  any 
non- volatile  soaps  or  soap-forming  ingredients.  Such  a 
material  may  be  diluted  with  water  and  applied  to  a  road 
surface  at  any  desired  rate.  It  is  primarily  of  value  as  a  dust 
preventive,  but  successive  applications  tend  to  fill  up  the  inter- 
stices of  the  road  surface  with  a  petroleum  residuum  which 
in  very  thin  layers  hardens  and  will  not  again  emulsify  with 
water.  The  asphaltic  character  of  the  material  is  shown  by 
its  percentage  of  asphaltenes  and  fixed  carbon. 


128       ANALYSES    OF    EMULSIFYING    OILS    AND    EMULSIONS 


The  other  two  emulsions  carry  even  a  higher  percentage  of 
water  than  the  residual  emulsion  because  they  have  been  pro- 
duced from  asphalt  cements  as  shown  by  the  penetrations  of 

TABLE  II 
ANALYSES  OF  EMULSIFYING  OILS  AND  EMULSIONS 


Test 

Emulsifying 
Oil 

Residual 
Emulsion 

Asphalt- 
Cement 
Emulsion 

Fluxed 
INative  Asph. 
Emulsion 

Sp  Gr  25°/25°C. 

O.076 

O.062 

O.Q7^ 

I  .OlS 

Sp.  Vis.,  Engler,  50  c.c., 
50°  C. 

23.6 

Flash  Point,  open  cup.  . 

173°  C. 

Loss,  105°  C.,  5  hrs.,  50 

IQ.0% 

24.76% 

52.5% 

Pen.  Res.,  25°  C.,  100 

t<.  ~  /u 
Viscous 

Sticky 

221 

195 

Loss,  163°  C.,  5  hrs.,  50 
grams  (additional) 

14.8% 

V4% 

Pen.  Res.,  25°  C.,  100 
8c  sec 

Fluid 

72 

Total  Bitumen  (Sol.  in 

CS2>                     

06.4.2% 

Tests  on 
Residue 

OQ.08% 

Tests  on 
Residue 

06.0O% 

Organic      matter      in- 
soluble   

O.22 

0.81 

1  .00 

Ash    as    alkaline    car- 
bonate 

1    16 

on 

I    2O 

Bit.  insol.  86°  B.  naph. 
(Asphaltenes) 

100.00% 
I    2% 

100.00% 
n  81% 

100.00% 
10  0% 

Fixed  Carbon 

0   6% 

4  28% 

IO  2% 

Approx.  Composition: 
Water 

21    4.1 

40.  SO 

Ammonium  (NHs) 

O.^S 

Fatty  and  Resin  Acids 

0-45 

Total  Bitumen 

36.  ^O 

Organic  matter  insol.. 
CSa  

I  .  IO 

Inorganic  matter.  .  .  . 

3.30 

100.00 

the  residues  obtained  from  the  volatilization  test  at  105°  C. 
Such  products  have  been  used  in  the  construction  of  cold-mixed 
bituminous  concrete  pavements,  but  when  so  used  a  very  con- 
siderable period  of  time  is  required  for  the  water  to  evaporate 
sufficiently  to  develop  the  necessary  consistency  of  bituminous 


NOTES 


NOTES 


ORDINARY    TESTS  129 

cement  which  such  highways  demand.  Their  greatest  value 
would  appear  to  lie  in  their  use  for  cold  mixes  to  be  used  in 
patching  bituminous  roads.  When  so  used  the  mix  hardens 
much  more  rapidly  than  when  laid  in  large  masses  as  in  con- 
struction work. 


SEMISOLID  AND   SOLID  PETROLEUM  AND 
ASPHALT  PRODUCTS 

Semisolid  petroleum  and  asphalt  products  are  used  as  asphalt 
cements  or  joint  fillers.  The  solid  products  are  usually  fluxed 
with  petroleum  residuums  to  produce  asphalt  cements  prior 
to  use. 

Asphalt  cements  intended  for  use  in  bituminous  macadam 
construction  are  generally  softer  than  for  bituminous  con- 
crete or  sheet  asphalt  pavements.  As  a  rule  the  finer  the 
mineral  aggregate  which  is  to  be  cemented  the  lower  should 
be  the  penetration  of  the  asphalt  cement.  This  is  due  to  the 
fact  that  compacted  fine  aggregate  possesses  less  resistance  to 
displacement  in  a  pavement  than  coarse  aggregate,  and  there- 
fore requires  a  more  solid  and  harder  cement  to  hold  the  mineral 
particles  in  place.  The  most  desirable  penetration  for  asphalt 
cements  for  a  given  type  of  pavement  varies  with  the  type 
of  oil  or  native  asphalt  from  which  they  are  produced,  and  the 
traffic  and  climatic  conditions  to  which  the  pavement  will  be 
subjected.  Asphalt  fillers  unless  especially  prepared  by  the 
addition  of  fine  mineral  matter  are  nothing  more  than  asphalt 
cements  particularly  adapted  to  waterproof  joints  as  the  pave- 
ment expands  and  contracts.  All  of  these  products  are  ordi- 
narily subjected  to  the  following  tests  for  the  purpose  of  iden- 
tification, control,  and  determination  of  their  suitability  for  a 
specific  purpose. 

ORDINARY   TESTS 

1.  Specific  Gravity  25° '/ 25°  C. 

2.  Penetration  Test: 

a.  Always  at  25°  C.,  100  grams,  5  seconds. 


130      INTERPRETATION  OF  RESULTS  IN  TABLE  HI 

b.  Frequently  at  o°  C.  or  4°  C.,  200  grams,  i  minute, 

when  used  in  cold  climates. 

c.  Sometimes  at  46°  C.,  50  grams,  5  seconds,  when  used 

with  fine  aggregates  or  as  fillers. 

3.  Melting  Point  °  C.  for  the  harder  varieties. 

4.  Ductility  at  25°  C.  sometimes  for  the  harder  varieties. 

5.  Flash  Point  °  C.  (usually  open  cup). 

6.  Volatilization  Test  at  163°  C.,  50  grams,  5  hours. 

7.  Penetration  of  Residue  from  Volatilization  Test,  penetration 

at  25°  C.,  100  grams,  5  seconds. 

8.  Total  Bitumen: 

Organic  Matter  Insoluble  in  Carbon  Bisulphide. 
Inorganic  Matter  Insoluble  in  Carbon  Bisulphide. 

9.  Asphaltenes. 

10.  Carbenes. 

11.  Fixed  Carbon. 


INTERPRETATION   OF   RESULTS    IN  TABLE  III 

Table  III,  on  page  131,  shows  the  results  of  these  tests 
upon  typical  oil  asphalts  or  asphalt  cements  and  fillers.  In 
comparing  test  values  it  should  be  remembered,  however, 
that  the  various  characteristics  of  the  asphalt  cements  are 
the  result  not  only  of  the  type  of  oil  distilled  but  also  of  the 
exact  method  of  distillation. 

Considering  first  the  three  Mexican  oil  asphalts,  it  will  be 
noticed  that  as  the  penetration  at  25°  C.  decreases  the  specific 
gravity,  melting  point,  flash  point,  asphaltenes,  and  fixed  car- 
bon increase.  On  the  other  hand,  the  penetration  at  o°  C.,  the 
ductility,  the  loss  at  163°  C.,  and  penetration  of  the  residue 
decrease.  The  solubility  in  carbon  disulphide  and  carbon  tetra- 
chloride,  however,  remain  about  the  same  as  they  are  all  prac- 
tically pure  bitumen  and  have  not  been  subjected  to  injurious 
cracking.  Their  penetration  at  25°  C.  would  represent  their 
relative  suitability  under  favorable  conditions  for  use  as  bitu- 
minous cements  in  the  construction  of  bituminous  macadam 
pavements,  coarse  aggregate  bituminous  concrete,  and  sheet 


NOTES 


NOTES 


ANALYSES    OF    OIL    ASPHALTS    AND    FILLERS 


131 


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132  INTERPRETATION    OF    RESULTS    IN    TABLE    III 

asphalt  topping.  A  somewhat  higher  penetration  than  that 
shown  by  No.  3  would  be  advisable  for  use  in  the  binder  course 
of  a  sheet  asphalt  pavement. 

The  relative  characteristics  of  oil  asphalts  from  different 
types  of  petroleums  are  illustrated  by  a  comparison  of  the 
Mexican  No.  2,  the  California,  and  the  Texas,  all  of  which 
"have  approximately  the  same  penetration  at  25°  C.  These 
products  show  evidence  of  having  been  manufactured  primarily 
by  careful  steam  distillation.  It  will  be  noted  that  for  approxi- 
mately the  same  consistency  there  is  a  general  decrease  in 
specific  gravity  from  the  Mexican  to  the  Texas  asphalt.  The 
California  asphalt  is  more  susceptible  to  temperature  changes 
than  are  the  other  two  as  shown  by  its  relative  penetration 
at  25°  C.  and  o°  C.  It  is  therefore  naturally  the  most  ductile. 
It  also  shows  the  lowest  per  cent  of  asphaltenes  and  fixed  car- 
bon, which  is  characteristic.  The  Mexican  asphalts  show  a 
typically  high  percentage  of  fixed  carbon.  The  flash  points  of 
all  three  products  are  over  205°  C.  and  their  low  loss  at  163°  C., 
together  with  the  penetration  of  their  residues,  well  above 
50%  of  the  original  materials,  show  that  they  will  not  unduly 
harden  during  their  manipulation  in  construction  or  under 
service  conditions. 

The  filler  which  is  produced  by  blowing  a  heavy  asphaltic 
residuum  shows  a  much  lower  specific  gravity  than  do  any 
of  the  other  materials,  although  its  penetration  is  the  lowest. 
It  has  a  higher  melting  point  and  is  much  less  susceptible  to 
temperature  changes,  as  shown  by  its  relative  penetration  at 
three  temperatures,  than  any  of  the  others.  Its  ductility  and 
percentage  of  fixed  carbon  are  low,  this  being  characteristic  of  all 
highly  blown  petroleums.  Its  percentage  of  asphaltenes  is  char- 
acteristically high.  Its  flash  point,  loss  at  163°  C.,  and  the 
relative  penetration  of  its  residue  are  similar  to  the  other 
asphalts.  As  a  filler  it  is  much  more  satisfactory  than  the 
other  materials  for,  existing  in  a  practically  pure  state  in  the 
pavement  joints,  it  will  not  become  unduly  hard  in  cold  weather 
nor  bleed  in  hot  weather.  The  blowing  process  may  be  used 
to  impart  to  a  petroleum  residuum  certain  desirable  charac- 


NOTES 


NOTES 


INTERPRETATION    OF    RESULTS    IN    TABLE    IV  133 

teristics,  from  the  standpoint  of  a  particular  use,  which  cannot  be 
secured  in  any  other  way.  Besides  being  particularly  adapted 
for  use  as  fillers,  blown  or  partly  blown  asphalts  of  the  type 
shown  are  admirably  adapted  for  use  as  seal-coating  mediums 
on  certain  types  of  coarse  aggregate  bituminous  concrete  pave- 
ments. If  of  suitable  consistency  their  peculiar  rubbery  nature 
makes  them  more  permanent  surfacing  materials  than  the 
straight  distilled  products. 

INTERPRETATION   OF   RESULTS  IN   TABLE   IV 

Table  IV,  on  page  134,  shows  the  results  of  tests  upon 
typical  refined  native  asphalts  of  most  importance  at  the 
present  time  and  of  certain  asphalt  cements  produced  by 
fluxing  them  with  residual  petroleums  or  fluxes.  It  should 
be  remembered  that  the  characteristics  of  asphalt  cements  pro- 
duced from  any  given  native  asphalt  may  be  largely  controlled 
not  only  by  the  amount  of  flux  but  also  by  the  type  of  flux  used. 
As  the  refined  native  asphalts  are  seldom  if  ever  used  without 
modification  in  highway  work,  it  is  seldom  considered  necessary 
to  make  or  report  all  tests  to  which  the  asphalt  cements  are 
ordinarily  subjected. 

Comparing  first  the  unfluxed  materials  it  will  be  seen  that 
the  refined  Trinidad  and  Cuban  asphalts  have  by  far  the  high- 
est specific  gravities.  This  is  due  to  their  very  high  percentage 
of  mineral  or  inorganic  matter  insoluble  in  carbon  disulphide. 
Refined  Trinidad  lake  asphalt  is  very  uniform  in  character, 
while  Cuban  asphalt  varies  considerably,  according  to  the  de- 
posit from  which  it  is  taken.  Refined  Bermudez  asphalt  has 
a  much  lower  specific  gravity  and  percentage  of  mineral  matter 
than  the  Trinidad  and  Cuban,  while  gilsonite,  which  is  prac- 
tically pure  bitumen,  has  the  lowest  specific  gravity  of  all.  The 
refined  Bermudez  has  the  highest  penetration  at  25°  C.,  the 
others  being  much  harder.  As  would  therefore  be  expected, 
the  Bermudez  showrs  the  lowest  percentage  of  asphaltenes. 
With  the  exception  of  Bermudez,  which  is  characteristically 
high  for  a  hard  R.  A.,  the  refined  native  asphalts  show  a  low 
loss  by  volatilization  at  163°  C.  The  percentage  of  bitumen 


134  ANALYSES  OF  NATIVE  ASPHALTS  AND  ASPHALT  CEMENTS 


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INTERPRETATION    OF    RESULTS    IN    TABLE    IV  135 

varies  from  almost  100  per  cent  in  the  case  of  gilsonite  to  as 
low  as  56.5%  in  the  case  of  Trinidad.  The  relative  percentages 
of  organic  and  inorganic  matter  insoluble  in  carbon  disulphide, 
together  with  the  character  of  such  matter,  helps  to  identify 
these  materials.  The  ash  of  Trinidad  asphalt,  particularly  the 
finer  portion,  is  characteristically  flesh  pink,  while  the  others 
are  brown  or  reddish  brown.  The  insoluble  organic  matter  of 
Bermudez  differs  from  the  others  in  that  it  consists  largely  of 
residues  of  vegetation,  such  as  very  fine  twigs,  veins  of  leaves 
or  grass,  etc.  Gilsonite  has  practically  no  insoluble  organic 
matter.  Little  or  no  carbenes  are  present  in  any  of  the  native 
asphalts  and,  in  fact,  both  the  Trinidad  and  Cuban  are  usually 
somewhat  more  soluble  in  carbon  tetrachloride  than  in  carbon 
disulphide.  The  percentage  of  fixed  carbon  varies  within  com- 
paratively narrow  limits  with  the  exception  of  the  Cuban,  which 
is  characteristically  high. 

As  compared  with  the  refined  asphalts  from  which  they  are 
produced,  the  asphalt  cements  or  fluxed  asphalts  in  general 
show  a  decided  decrease  in  specific  gravity  and  asphaltenes  with 
an  increase  in  penetration  and  percentage  of  total  bitumen. 
This  is  what  would  be  expected  from  the  fact  that  the  flux  is 
usually  a  viscous  fluid  residual  petroleum  consisting  of  prac- 
tically pure  bitumen  with  a  lower  specific  gravity  and  percent- 
age of  asphaltenes  than  the  refined  asphalt.  As  specific  grav- 
ity is  usually  an  additive  property  in  mixtures  of  bituminous 
materials  if  the  specific  gravity  of  the  original  R.  A.  and  flux, 
together  with  that  of  the  A.  C.,  are  known,  the  approximate 
properties  of  R.  A.  and  flux  may  be  calculated.  The  same 
is  true  of  the  percentage  of  bitumen.  If,  therefore,  a  refined 
asphalt  is  uniform  in  character  it  may  be  possible  to  calculate 
from  the  total  bitumen  of  its  A.  C.  alone  how  much  flux  has 
been  used.  In  such  case  the  flux  is  presumed  to  be  pure  bitumen. 

The  penetration  of  a  fluxed  asphalt  will  necessarily  depend 
to  a  large  extent  upon  the  type  of  flux  and  the  amount  used. 
The  more  of  a  given  flux  which  is  combined  with  an  asphalt 
the  higher  becomes  the  penetration  of  the  asphalt  cement. 
Also,  in  general,  the  heavier  the  flux  the  more  is  required  to 


136 


FLUXING    ASPHALTS 


produce  an  asphalt  cement  of  given  penetration  from  a  given 
asphalt.  Light  fluxes  prepared  from  a  given  petroleum  as  a 
rule  produce  asphalt  cements  less  susceptible  to  temperature 
changes  than  do  the  heavier  fluxes  produced  from  the  same 
petroleum,  but  they  are  apt  to  show  a  higher  loss  by  volatiliza- 
tion. Fluxes  which  are  suitable  for  one  asphalt  will  not  always 
produce  satisfactory  asphalt  cements  from  another  asphalt. 
It  is  therefore  frequently  advisable  to  study  various  combina- 


w 

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/ 

/ 

/ 

/ 

/ 

/ 

£j    40    60    80    100   120   140   160   180   200   22 

Penetration  25°  C.  100  Grams -5  Sec. 
FIG.  39.     Example  of  Fluxing  Curve 

tions  in  the  laboratory  before  making  up  large  batches  of  asphalt 
cement  in  the  plant  or  factory. 

While  experience  will  often  indicate  the  proportion  of  a  given 
flux  to  add  to  a  refined  asphalt  in  order  to  produce  an  asphalt 
cement  of  any  desired  penetration,  it  is  often  desirable  to  pre- 
pare a  fluxing  curve  in  the  laboratory.  This  is  done  by  making 
up  a  number  of  trial  mixes  of  known  proportions  and  plotting 
the  penetrations  of  the  resulting  asphalt  cements  against  the 
parts  of  flux  used  to  100  parts  of  the  refined  asphalt,  as  shown 
in  Fig.  39.  If  these  mixtures  have  been  properly  selected  it 
will  then  be  possible  to  construct  from  these  plotted  points  a 
curve  from  which  may  be  obtained  with  reasonable  accuracy 
the  amount  of  the  given  flux  to  use  if  it  is  desired  to  secure 
an  asphalt  cement  of  a  given  consistency. 


NOTES 


NOTES 


REFINED    TARS    AND    TAR    PITCHES  137 

The  value  of  this  method  at  once  becomes  apparent  when 
it  is  realized  that  to  produce  an  asphalt  cement  of  50  penetra- 
tion from  refined  Trinidad  asphalt  may  usually  require  from 
20  to  60  parts  of  flux  per  hundred,  while  in  the  case  of  refined 
Bermudez  from  9  to  30  parts  only  may  be  required  to  produce 
an  asphalt  cement  of  the  same  penetration. 

No  matter  how  large  a  proportion  is  used,  a  good  flux  should 
not  materially  raise  the  loss  at  163°  C.  of  an  asphalt  nor  should 
it  tend  to  harden  to  such  an  extent  as  to  cause  the  residue  of 
the  asphalt  cement  to  exhibit  an  undue  decrease  in  penetration. 
Of  the  asphalt  cements  shown  in  the  table  it  will  be  noticed 
that  in  the  case  of  Bermudez  the  loss  by  volatilization  has 
even  been  decreased  by  the  addition  of  flux.  Like  the  oil 
asphalts,  fluxed  native  asphalts  of  various  consistencies  are 
required  for  the  different  types  of  construction. 

Cuban  asphalts  and  gilsonite  are  less  used  in  the  United 
States  for  road  and  paving  purposes  than  are  Trinidad  and 
Bermudez  asphalts.  Gilsonite,  has,  however,  to  a  considerable 
extent  been  combined  with  relatively  large  quantities  of  blown 
petroleum  residuums  to  form  what  are  known  as  blown-oil 
gilsonite  products,  which  are  cementitious  and  possess  a  very 
marked  rubbery  characteristic. 


REFINED  TARS  AND  TAR  PITCHES 

• 

Refined  tars  are  used  as  dust  preventives,  carpeting  mediums, 
or  bituminous  cements,  largely  according  to  their  consistency. 
The  bituminous  cements  are  usually  soft  pitches,  while  the 
harder  tar  pitches  are  sometimes  used  as  joint  fillers. 

Crude  tars  are  sometimes  used  as  dust  preventives.  Most 
coal  tars  are,  however,  too  viscous  for  successful  cold  applica- 
tion and  have  to  be  combined  with  distillates  or  very  fluid 
tars  in  order  to  make  them  applicable  for  such  work.  Water- 
gas  tars  and  some  coke-oven  tars  may,  however,  be  applied 
cold  in  the  crude  or  partially  dehydrated  state.  High  carbon 
tars  are  totally  unsuited  for  use  as  dust  preventives,  and  the 


138  REFINED    TARS    AND    TAR    PITCHES 

majority  of  the  dust  preventives  are,  therefore,  generally  manu- 
factured from  low  carbon  crudes.  In  order  to  so  use  tars  con- 
taining as  high  as  5  per  cent  of  free  carbon,  it  is  not  unusual 
to  have  them  combined  with  a  small  amount  of  water,  which 
increases  their  fluidity  or,  in  other  words,  decreases  their  vis- 
cosity. Partly  dehydrated  coke-oven  tars  combined  with  water- 
gas  tars  may  be  made  to  serve  this  purpose.  Owing  to  the  fact 
that  the  dust  preventives  tend  to  volatilize  and  harden  more 
rapidly  than  petroleum  dust  preventives,  their  excessive  use 
is  not  so  apt  to  disintegrate  the  road  through  lubrication.  Their 
repeated  use  may,  moreover,  result  in  the  formation  of  a  thin 
bituminous  carpet. 

Tar  carpeting  mediums  are  usually  straight  distilled  residual 
tars  which  are  too  viscous  to  apply  cold.  They  ordinarily  pos- 
sess more  cementitiousness  than  a  petroleum  product  of  similar 
viscosity  and  harden  more  rapidly  after  application  to  a  road 
surface.  If  used  in  excess,  however,  they  are  apt  to  produce 
with  the  covering  of  mineral  matter  an  unstable  and  wavy 
carpet.  Their  initial  hardening,  which  is  a  desirable  feature, 
is,  under  ordinary  conditions,  apt  to  continue  until  the  carpet 
becomes  so  hard  that  it  wears  more  rapidly  under  traffic  than 
does  the  petroleum  carpet.  This  is  particularly  true  of  those 
materials  which  contain  a  high  percentage  of  the  lighter  oils 
or  naphthalene  and  free  carbon.  For  carpet  work  this  general 
tendency  to  harden  even  too  much  is  preferable  to  not  harden- 
ing sufficiently.  In  some  cases  petroleum  or  asphalt  products 
are  combined  in  relatively  small  proportions  with  tar  carpeting 
mediums,  in  order  to  reduce  the  tendency  to  harden. 

Because  of  their  tendency  to  harden  after  use  and  their 
susceptibility  to  temperature  changes,  the  refined  tars  used  in 
bituminous  macadam  and  bituminous  concrete  pavements  are 
usually  much  softer  than  either  the  oil  asphalts  or  fluxed  native 
asphalts  used  in  the  same  type  of  construction.  This  is  ad- 
missible when  the  aggregate  is  coarse,  because  of  the  high 
cementitiousness  of  the  soft  semisolid  tars  residues.  For  fine 
aggregates  where  mechanical  stability  is  largely  dependent  upon 
the  hardness  of  the  bituminous  cement,  tars  are  notgenerallyused. 


NOTES 


NOTES 


ORDINARY    TESTS  139 

For  the  coarser  aggregate  pavements  the  same  grade  of  tar 
used  in  the  construction  of  the  wearing  course  proper  is 
also  commonly  used  as  a  seal  coat.  Although  such  a  seal 
coat  is  apt  to  harden  more  rapidly,  perhaps,  than  desirable,  in 
the  case  of  the  bituminous  macadam  the  underlying  thick  films 
of  tar  tend  to  enrich  and  prolong  the  life  of  the  seal  coat.  In 
bituminous  concrete  construction,  however,  there  is  not  the 
same  excess  of  bitumen  in  the  underlying  course,  and  for  this 
reason  an  asphalt  seal  coat  is  sometimes  employed  where  a 
refined  tar  is  used  in  the  concrete  proper. 

Pitch  fillers  are  manufactured  from  tars  by  distillation  and 
sometimes  blowing  the  tar  residue  to  the  desired  melting  point. 
They  are  often  quite  hard  and  brittle  and  carry  to  advantage  a 
high  percentage  of  free  carbon.  They  are  much  more  susceptible 
to  temperature  changes  than  are  the  blown  petroleum  or  asphalt 
products  prepared  for  the  same  purpose. 

The  refined  tars  and  tar  pitches  are  ordinarily  subjected  to 
the  following  tests  in  routine  examination: 

ORDINARY  TESTS 

1.  Specific  Gravity  25°/25°  C. 

2.  Specific  Viscosity  (Engler)  50  cubic  centimeters  at  40°  or  50° 

C.  for  materials  for  cold  surface  application. 

3.  Float  Test  at  50°  C.  for  materials  which  have  to  be  heated, 

except  the  hard  tar  pitches. 

4.  Penetration  Test  at  25°  C.,  100  grams,  5  seconds,  for  hard 

tar  pitches. 

5.  Melting  Point  °  C.,  cube  method,  for  the  harder  tar  pitches. 

6.  Distillation  Test  (flask  method): 

Water. 

Distillate  to  110°  C. 
Distillate  no°-i7o°  C. 
Distillate  ifjo°-2fjo°  C. 
Distillate  270°  -300°  C. 
Pitch  Residue. 

7.  Melting  Point  °C.  (cube  method)  of  residue  from  distillation 

test. 


140  INTERPRETATION    OF    RESULTS    IN    TABLE    V 

8.  Total  Bitumen: 

Organic  Matter  Insoluble  in  Carbon  Bisulphide  (freecarbon). 
Inorganic  Matter  Insoluble  in  Carbon  Bisulphide. 

9.  Dimethyl  sulphate  test  when  the  presence  of  petroleum  or 

asphalt  products  is  required  or  suspected. 

INTERPRETATION  OF  RESULTS  IN  TABLE  V 

Table  V,  on  page  141,  shows  the  results  of  these  tests 
upon  typical  tar  products  prepared  for  use  in  highway  work 

In  comparing  these  analyses  it  will  first  be  noticed  that  for 
the  same  purpose  refined  water-gas  tars  show  a  lower  specific 
gravity  and  a  lower  percentage  of  free  carbon  than  do  the  others. 
If  the  three  water-gas  tars  are  considered  it  will  also  be  seen 
that  their  specific  gravities  increase  as  they  become  more  vis- 
cous and  show  a  higher  float  test. 

The  first  analysis  is  that  of  a  dust  preventive  produced  from 
a  water-gas  tar  by  distillation  of  the  more  volatile  constituents. 
The  second  is  one  produced  from  a  low  carbon  coal  tar  and 
shows  the  presence  of  both  water  and  light  oils.  The  water 
is  largely  responsible  for  the  low  specific  viscosity  of  this 
material  as  compared  with  the  first  sample.  Its  specific  grav- 
ity and  percentage  of  free  carbon  indicate  a  coke-oven  tar. 
Both  products  show  practically  the  same  amount  of  pitch  residue. 
It  has  been  found  that  in  general  refined  tars  with  as  high 
as  30  specific  viscosity  at  50°  C.  may  be  successfully  applied 
cold.  Both  products  are  therefore  suitable  for  cold  application. 

The  first  carpeting  medium  is  a  tar  asphalt  compound  as 
evidenced  by  the  positive  result  of  the  dimethyl  sulphate  test. 
Its  specific  gravity  and  very  low  percentage  of  free  carbon  show 
it  to  be  largely  a  refined  water-gas  tar.  The  second  product 
contains  no  petroleum  or  asphalt  as  shown  by  the  negative 
result  from  the  dimethyl  sulphate  test.  Its  percentage  of  free 
carbon  comes  just  within  the  maximum  limit  for  what  is  con- 
sidered the  best  type  of  tar  carpeting  medium.  Its  float  test 
at  50°  C.  is  lower  than  for  the  water-gas  tar,  although  it  has 
a  higher  percentage  of  pitch  residue.  This  is  due  to  the  fact 


NOTES 


NOTES 


ANALYSES    OF    REPINED    TARS 


141 


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142  INTERPRETATION    OF    RESULTS    IN    TABLE    V 

that  the  actual  percentage  of  bitumen  in  its  pitch  residue  is 
much  lower  and  it  therefore  contains,  on  a  bitumen  basis,  a 
much  greater  proportion  of  oils  distilling  below  300°  C. 
While  originally  softer,  it  would  therefore  tend  to  harden  more 
rapidly  in  service  than  the  water-gas  tar  product.  This  is  fur- 
ther indicated  by  the  higher  melting  point  of  its  pitch  residue. 
As  shown  by  their  float  test,  both  products  possess  a  satisfac- 
tory original  consistency  for  building  up  a  bituminous  carpet 
and  would  have  to  be  applied  in  a  heated  state. 

Refined  tars  used  as  cements  in  bituminous  macadam  or 
coarse  aggregate  bituminous  concrete  pavements  usually  show 
a  float  test  at  50°  C.  of  from  2  to  3  minutes.  All  of  the  last 
three  products  come  within  these  limits.  Although  of  similar 
consistency,  it  will  be  noted  that  the  residual  water-gas  tar 
shows  the  lowest  percentage  of  free  carbon  and  the  residual 
gas-house  coal  tar  the  highest.  The  specific  gravity  of  these 
tars  increases  with  the  percentage  of  free  carbon.  All  of  the 
materials  show  a  very  low  percentage  of  ash,  and  the  percent- 
age of  total  bitumen  is  therefore  almost  entirely  dependent 
upon  the  amount  of  free  carbon  present.  All  of  the  residuals 
have  been  prepared  at  sufficiently  high  temperatures  to  remove 
the  more  volatile  oils,  as  shown  by  the  results  of  distillation. 
The  relation  of  total  distillate  to  pitch  residue  is  found  to  vary 
somewhat  but  the  ratio  of  total  distillate  to  actual  bitumen  in 
the  pitch  residue  will,  upon  calculation,  be  found  to  be  nearly 
the  same.  In  this  connection  it  should  be  remembered  that 
all  of  the  free  carbon  concentrates  in  the  residue  during  dis- 
tillation. If,  for  example,  the  original  crude  tar  contains  10 
per  cent  of  free  carbon  and  the  pitch  residue  amounts  to  50 
per  cent  of  the  crude,  that  residue  would  then  consist  of  not 
less  than  20  per  cent  or  one-fifth  free  carbon. 

Free  carbon  in  tars  exists  in  the  form  of  finely  divided 
amorphous  black  particles  resembling  soot  or  lamp-black.  These 
particles  are  held  in  suspension  in  the  tar  and  will  not  readily 
settle  out  even  if  the  tar  is  very  fluid.  If  filtered  from  the 
bitumen  the  free  carbon  is  found  to  be  a  dry  black  powder  en- 
tirely lacking  in  cementitiousness.  Ultimate  analysis  indicates 


NOTES 


NOTES 


FREE    CARBON    IN    TARS  143 

that  it  is  not,  however,  pure  carbon  but  probably  a  mixture 
of  hydrocarbons  very  rich  in  carbon,  .which  have  been  produced 
by  an  advanced  stage  of  cracking  during  the  original  formation  of 
the  tar.  For  all  practical  purposes,  however,  it  may  be  con- 
sidered as  carbon  and  as  an  inert  impurity  in  the  tar  bitumen. 
It  is  non- volatile  at  ordinary  distilling  temperatures,  and  for  this 
reason  always  remains  in  the  residue  of  a  tar  distillation.  As  a 
very  high  percentage  of  free  carbon  is  not  considered  desirable 
in  refined  tars  commonly  used  in  highway  engineering,  those 
crude  tars  which  originally  carry  a  high  percentage  can- 
not well  be  utilized  in  the  manufacture  of  such  products 
unless  mixed  in  suitable  proportions  with  a  low  carbon  crude 
tar  prior  to  distillation.  If  both  low  and  high  carbon  tars  are 
available  to  the  tar  refiner  he  is  able  by  judicious  mixing  to 
obtain  a  combination  which  upon  subsequent  distillation  will 
yield  a  refined  tar  containing  less  than  the  maximum  limit  of 
free  carbon  which  has  been  set.  Knowing  the  per  cent  of  dis- 
tillate which  will  have  to  be  removed  in  order  to  produce  a 
residue  of  desired  consistency,  the  percentage  of  free  carbon 
in  the  refined  tar  may  be  closely  approximated  from  the  per- 
centage present  in  the  material  distilled.  If,  however,  the  tar 
is  badly  cracked  or  locally  overheated  during  distillation,  addi- 
tional free  carbon  will  be  formed.  As  all  tars  originally  con- 
tain some  free  carbon,  however,  it  is  impossible  from  its  deter- 
mination in  the  finished  product  to  ascertain  whether  or  not 
cracking  has  taken  place  during  distillation  as  in  the  case  of 
petroleum  products.  While  chemically  inert,  free  carbon  has 
a  decided  effect  upon  certain  physical  characteristics  of  the  tar 
in  which  it  occurs.  It  increases  the  gravity  of  a  tar  and  also 
its  viscosity  or  apparent  consistency  to  a  marked  extent.  In  a 
general  comparison  of  low  and  high  carbon  tars  the  following 
facts  are  of  interest  to  the  highway  engineer.  For  refined  tars 
of  the  same  degree  of  hardness  those  of  low  free  carbon  con- 
tents have  greater  inherent  binding  strength  than  those  of  high 
carbon  contents.  In  refined  tars  whose  bitumen  is  of  the  same 
degree  of  hardness  these  high  in  free  carbon  have  a  greater 
inherent  binding  strength  than  those  low  in  free  carbon,  but 


144  NAPHTHALENE    IN    TARS 

i 

the  binding  capacity  of  the  former  is  lower  because  of  the  lower 
percentage  of  bitumen  present.  The  waterproofing  value  of 
high  carbon  tars  is  in  general  less  than  that  of  low  carbon  tars. 
A  high  percentage  of  free  carbon  tends  to  retard  absorption  of 
the  tar  bitumen  by  porous  surfaces.  When  a  tar  is  exposed  in 
comparatively  thin  films  free  carbon  has  little  or  no  effect  in 
retarding  volatilization  of  the  lighter  bituminous  constituents. 
In  certain  classes  of  tar  aggregates  free  carbon  may  serve  as 
a  filler  and  add  to  the  mechanical  strength  of  the  aggregate, 
but  finely  divided  mineral  matter,  which  may  be  incorporated 
in  any  desired  amount,  is  more  satisfactory  in  this  connection. 
In  general  it  is  considered  desirable  that  a  tar  dust  layer  should 
not  contain  over  8%  free  carbon,  that  a  tar  carpeting  medium 
should  not  contain  over  15%  free  carbon,  and  that  for  bitumi- 
nous macadam  and  bituminous  concrete  construction  a  refined 
tar  should  not  contain  over  20%  free  carbon.  There  is,  however, 
some  difference  of  opinion  in  this  connection. 

Naphthalene,  CioHs,  frequently  occurs  in  tar  in  larger  quan- 
tity than  any  other  one  hydrocarbon  and  for  this  reason  it 
exerts  an  appreciable  influence  upon  the  physical  and  chemical 
properties  of  the  tar.  In  the  pure  state  it  exists  in  white  flaky 
crystals  or  scales  melting  at  79°  C.  and  having  a  boiling  point 
of  218°  C.  It  has  the  characteristic  odor  commonly  familiar 
in  moth  balls  and  is  extremely  volatile.  It  volatilizes  far  below 
its  boiling  point  and  from  crude  tars  distills  to  a  considerable 
extent  with  the  aqueous  vapors  and  also  with  the  light  tar  oils. 
Even  at  ordinary  temperatures  it  volatilizes  slowly  from  both 
crude  tars  and  refined  tars  in  which  it  is  present.  No  satis- 
factory method  has  as  yet  been  devised  for  its  quantitative 
determination  in  tars,  but  its  presence  in  appreciable  quantities 
is  readily  detected  by  its  crystallization  from  certain  fractions 
obtained  by  distilling  the  tar.  In  some  tars  it  occurs  to  such 
a  large  extent  that  almost  the  entire  distillate  solidifies  or  crys- 
tallizes upon  cooling.  In  the  manufacture  of  straight  residual 
refined  tars  for  use  in  highway  engineering  some  of  the  naph- 
thalene is  removed  during  distillation.  A  considerable  propor- 
tion, however,  usually  remains  behind  in  the  residue.  The  pres- 


NOTES 


NOTES 


CREOSOTING    OILS    OR    WOOD    PRESERVATIVES  145 

ence  of  this  naphthalene  exerts  a  marked  influence  upon  the 
consistency  of  the  tar  and,  as  it  is  a  volatile  constituent,  its  effect 
in  this  connection  is  of  considerable  interest.  From  its  nature 
it  cannot  be  considered  as  a  binding  constituent,  but,  although 
it  is  solid,  it  may  combine  with  and  serve  as  a  flux  for  those 
hydrocarbons  which  are  directly  responsible  for  the  cementi- 
tiousness  of  tars.  Thus  by  heating  together  a  quantity  of  naph- 
thalene and  a  hard  tar  pitch  it  is  often  possible  to  produce  a  soft 
and  almost  fluid  product.  In  this  connection  it  has  been  found 
that  the  fluxing  value  of  naphthalene  for  hard  tar  pitches  is  some- 
what greater,  although  quite  similar  to  the  heavier  tar  distillates 
free  from  naphthalene  or  other  crystallizable  solids.  This  is  true 
until  the  mixture  becomes  so  saturated  as  to  cause  the  naphthalene 
to  precipitate.  For  the  harder  tar  pitches  the  addition  of  very 
small  percentages  of  naphthalene  produces  a  more  marked  in- 
crease in  fluidity  than  for  originally  softer  pitches.  On  the  other 
hand  where  naphthalene  is  present  beyond  its  point  of  satura- 
tion it  decreases  the  fluidity  of  the  product  at  temperatures 
below  its  melting  point,  but  at  higher  temperatures  it  continues 
to  increase  the  fluidity  of  the  product.  The  conclusions  to  be 
drawn  from  the  above  facts  are  that  refined  tars  containing  a 
high  percentage  of  naphthalene,  although  the  lighter  tar  oils 
may  be  absent,  may  be  expected  to  harden  rapidly  upon  expo- 
sure through  loss  of  the  naphthalene  by  volatilization.  This 
is  particularly  true  when  the  refined  tar  is  used  for  surface 
treatment. 


CREOSOTING  OILS  OR  WOOD  PRESERVATIVES 

There  is  probably  no  class  of  bituminous  materials  over 
which  there  is  a  wider  diversity  of  opinion  relative  to  desirable 
characteristics  than  creosoting  oil  or  wood  preservatives.  The 
oldest  and  apparently  the  most  favored  type  are  the  coal-tar 
distillates.  There  are,  however,  a  growing  number  of  advo- 
cates of  water-gas  tar  oils  and  of  fluid  refined  tars  or  mixtures 
of  refined  tars  with  tar  distillates. 


146 


ORDINARY    TESTS 


OEDINARY   TESTS 

The  wood  preservatives  are  now  commonly  subjected  to  the 
following  tests: 

1.  Specific  Gravity  38738°  C. 

2.  Specific  Viscosity  (Engler)  82°  C. 

3.  Material  insoluble  in  Benzol  and  Chloroform. 

4.  Water. 

5.  Distillation  Test  (Retort  Method): 

Distillate  2oo°-2io°  C. 
2io°-235°  C. 

"  23  C°— *TC°  C 

235       O1^      *— 

3T-5°-355°  C- 
Residue  (Character). 

6.  Specific  Gravity  38°  C.  of  Distillate  from  235°  to  315°  C. 

7.  Specific  Gravity  38°  C.  of  Distillate  from  315°  to  355°  C. 

An  idea  of  the  two  most  common  types  of  wood  preserva- 
tives may  perhaps  best  be  obtained  from  Table  VI,  which  is  an 
abstract  of  two  specifications  published  in  the  1916  report  of 
Committee  D-y  of  The  American  Society  for  Testing  Materials. 


TABLE  VI 
SPECIFICATION  LIMITS  FOR  WOOD  PRESERVATIVES 


Test 

Coal-Tar 
Oil 

Water-Gas 
Tar  Oil 

Sp  Gr.  38°/38°  C  

I.O6-I  .12 
Not  over    1  .  3 

Not  over    3.0% 
Not  over    3.0% 

Not  over    5.0% 
Not  over  30  .  o% 
35.0-70.0% 
Not  under  65.0% 

Not  under  1  .  02 
Not  under  1  .  08 

I.  I  I-I.I4 

Sp  Vis.  (Engler)  82°  C  

Material  insol.  hot  benzol,  chloro- 
form   
Water  
Distillation  (Retort  Method) 
Up  to  210°  C.,  by  weight  
Up  to  235°  C.,  by  weight  
Up  to  315°  C.,  by  weight  

Not  over    2.0% 

Not  over    3.0% 
Not  over  10.0% 
Not  over  40.0% 
Not  under  25.0% 

0.96-1.00 

Up  to  355°  C.,  by  weight  

Sp.  Gr.  38°  C.  of   Distillate   from 
235°  to  315°  C  

Sp.   Gr.  38°  C.   of   Distillate  from 
-us;0  to  iss°C. 

NOTES 


NOTES 


BITUMINOUS    AGGREGATES  147 

INTERPRETATION  OF  RESULTS  IN  TABLE  VI 

In  comparing  these. test  values  it  will  be  noted  that  while 
the  specific  gravity  of  the  water-gas  tar  oil  is  allowably  higher 
than  the  coal-tar  oil,  the  specific  gravity  of  its  distillate  from 
235°  to  315°  C.  is  much  lower.  This  practically  prevents  a 
mixture  of  appreciable  quantities  of  one  type  with  another. 
The  specific  gravity  of  the  water-gas  tar  oil  practically  neces- 
sitates the  presence  of  a  considerable  quantity  of  pitch  while 
that  of  the  coal-tar  oil  requires  a  large  amount  of  coal-tar  dis- 
tillate and  allows  for  a  relatively  small  amount  of  coke-oven 
tar  pitch  or  an  exceedingly  small  proportion  of  gas-house  tar 
pitch.  The  latter  is  further  restricted  by  the  3.0%  allowance 
for  insoluble  material.  In  neither  case  does  the  allowance  for 
insoluble  material  reach  a  percentage  which  would  seriously 
interfere  with  the  impregnation  of  wood  block  through  undue 
clogging  of  the  cells.  The  distillation  limits  hi  general  indicate 
that  the  coal-tar  oil  is  more  volatile  and  would  therefore  tend 
to  evaporate  more  rapidly  from  the  block.  On  the  other  hand 
it  would  produce  a  cleaner  and  less  sticky  block  owing  to  its 
lower  percentage  of  pitch.  The  relative  value  of  oils  covered 
by  these  specifications  for  waterproofing  and  preserving  wood- 
paving  block  and  producing  a  satisfactory  pavement  would 
depend  both  upon  their  manipulation  during  the  impregnating 
process  and  upon  conditions  to  which  the  finished  pavement 
would  be  subjected. 

BITUMINOUS  AGGREGATES 

Bituminous  aggregates  are  ordinarily  examined  only  for  the 
percentage  of  bitumen  and  the  mechanical  analysis  or  grading 
of  the  mineral  aggregate  which  may  either  be  reported  upon  a 
percentage  basis  of  the  original  mix  or  upon  the  mineral  matter 
alone.  In  some  cases  it  is  advisable  to  recover  the  bitumen  for 
the  purpose  of  identification  and  frequently  for  its  specific 
gravity.  The  specific  gravity  of  the  mineral  matter  may  also  be 
determined  to  advantage. 


148  RATIONAL    PER    CENT    OF    BITUMEN 

RATIONAL  PER   CENT   OF   BITUMEN 

The  .determination  of  the  percentage  of  bitumen  as  ordi- 
narily made  is  upon  a  weight  basis.  As  a  means  of  com- 
paring different  bituminous  aggregates  the  weight  basis 
is  irrational  unless  the  relations  of  weight  to  volume  are  the 
same  for  the  mixtures  compared.  In  any  bituminous  aggregate 
the  volume  of  bitumen  is  a  most  important  factor  from  the 
standpoint  of  covering  capacity,  thickness  of  film,  and,  in  some 
cases,  the  reduction  of  voids.  In  view  of  the  rather  wide  varia- 
tion in  specific  gravity  of  ordinary  bituminous  cements  and 
mineral  aggregates  the  volume  method  of  comparison  is  the 
most  rational.  The  volume  or  rational  per  cent  of  bitumen 
in  a  bituminous  aggregate  may  be  determined  by  recovery  of 
the  bitumen  after  its  extraction  and  determination  upon  a 
weight  basis.  The  specific  gravity  of  the  recovered  bitumen 
should  be  determined  as  well  as  that  of  the  mineral  aggregate. 
From  this  data  the  volume  proportions  of  each  are  ascertained 
by  dividing  their  weight  per  cent  by  their  respective  specific 
gravity.  These  proportions  transposed  to  total  100  are  the 
rational  or  volume  percentages  of  the  constituents.  The  formula 
for  expressing  the  rational  per  cent  of  bitumen  is  as  follows, 
where  x  represents  the  rational  per  cent  of  bitumen,  p  the 
weight  per  cent  of  bitumen,  a  the  specific  gravity  of  the  bitu- 
men, and  b  the  specific  gravity  of  the  aggregate: 

100  pb 


pb-\-a  (100  —  p) 

The  importance  of  the  use  of  the  rational  per  cent  of  bitumen 
as  a  basis  of  comparison  may  be  illustrated  by  considering  two 
bituminous  aggregates  which  contain  6%  by  weight  of  bitumen 
and  are  practically  identical  in  so  far  as  the  consistency  of 
bitumen  and  grading  of  the  aggregates  are  concerned.  Accord- 
ing to  the  ordinary  interpretation  of  results  of  analysis  the 
two  mixtures  might  be  considered  as  equivalents.  If,  however, 
it  is  found  that  the  first  mix  is  composed  of  an  aggregate  with 


NOTES 


NOTES 


DENSITY    AND    VOIDS  149 

a  specific  gravity  of  2.50  while  the  recovered  bitumen  shows 
a  specific  gravity  of  1.17  and  that  the  aggregate  of  the  second 
mix  has  a  specific  gravity  of  3.50  while  the  recovered  bitumen 
shows  a  specific  gravity  of  0.960,  the  rational  per  cent  of  bitumen 
would  be  found  to  differ  greatly  in  the  two  mixes,  as  follows: 

Rational  Rational 

Constituents          %  by  Wt.  Sp.  Gr.  Proportion  % 

First  mix: 

Aggregate 94         -=-         2.50         =         37.6  =  88.0 

Bitumen 6         -f-         I-I7          =  5-1  =  12.0 


100  100.00 


Second  mix: 

Aggregate 94         -f-         3.50          =         26.9          =  81.0 

Bitumen 6         •£•         0.96         =  6.3         =  19.0 


100  IOO.O 


DENSITY  AND   VOIDS 


Without  reference  to  grading  or  practical  possible  compres- 
sion, the  theoretical  maximum  density  of  a  compressed  bitu- 
minous aggregate  may  be  calculated  from  the  specific  gravity 
and  relative  proportions  of  the  individual  constituents  present. 
Where  the  individual  constituents  are  at  first  hand  this  is  a 
comparatively  simple  matter,  but  where  a  mixed  aggregate  or 
section  of  compressed  pavement  is  under  examination  it  is 
first  necessary  to  remove  and  recover  the  bitumen,  the  per- 
centage of  which  must  also  be  determined.  The  specific  gravity 
of  recovered  bitumen  may  then  be  determined  and  that  of  the 
mineral  aggregate.  If  coarse  particles  are  present  it  is  advis- 
able to  screen  the  aggregate  into  two  or  more  sizes  and  deter- 
mine the  specific  gravity  of  each.  After  the  gravity  and  per 
cent  by  weight  of  the  various  constituents  have  been  deter- 
mined, their  volume  proportions  are  calculated  by  dividing  their 
weight  percentages  by  their  respective  specific  gravities.  The 
ratio  of  the  sum  of  the  weight  proportions  to  the  sum  of  the 
volume  proportions  is  then  the  theoretical  maximum  density 
of  the  mix.  When  the  per  cent  by  weight  and  specific  gravity 
of  two  or  three  constituents  are  given,  the  following  formulas 
may  be  used  if  D  represents  the  maximum  possible  density, 


150  DENSITY    AND    VOIDS 

IF,  Wl  and  TF2  represent  the  per  cents  by  weight  and  G,  Gl  and 
G2  their  respective  specific  gravities. 

Two  Constituents  Three  Constituents 


~  W      W*  ~  W      W1      W* 

^"""G1  <f  ""G*""  G2 

The  probable  maximum  density  of  compressed  bituminous 
aggregates  may  be  determined  experimentally  in  the  laboratory 
by  heating  the  mixed  aggregate  to  proper  working  temperature 
and  compressing  it  in  a  cylindrical  mold  fitted  with  a  plunger 
which  has  also  been  heated  to  the  same  temperature.  The 
plunger  may  be  forced  into  the  mold  by  means  of  a  compres- 
sion machine  or  heavy  hammer.  Upon  cooling,  the  specimen 
is  forced  from  the  mold  and  its  specific  gravity  determined  by 
the  ordinary  displacement  method.  The  probable  maximum 
density  is  largely  dependent,  upon  the  grading  of  the  mineral 
particles,  which  is  a  most  important  consideration  for  fine  aggre- 
gates. For  a  well-graded  fine  aggregate  carrying  the  proper 
percentage  of  bituminous  cement  the  probable  maximum  den- 
sity should  closely  approach  the  theoretical  maximum  density. 

The  actual  density  of  compressed  bituminous  aggregate,  such 
as  a  section  of  a  bituminous  concrete  pavement,  is  directly 
determined  by  means  of  the  displacement  method.  If  satis- 
factory compression  has  been  obtained  in  the  construction  of 
the  pavement,  its  density  should  closely  approach  the  probable 
maximum  density  as  obtained  by  laboratory  test  upon  a  sec- 
tion of  the  pavement  which  is  first  softened  and  disintegrated 
by  warming  and  then  compressed  at  proper  working  temperature 
as  described  in  the  preceding  paragraph. 

The  per  cent  of  voids  in  a  compressed  bituminous  aggregate 
is  determined  from  the  actual  density  of  the  compressed  aggre- 
gate as  compared  with  the  theoretical  maximum  density,  which 
allows  for  no  voids.  Thus,  if  D  represents  the  theoretical  maxi- 
mum density  and  d  the  actual  density,  the  per  cent  of  voids  is 
determined  by  the  following  formula: 

~  100  (D  -  d) 

%  Voids  =  -      ^— 


NOTES 


NOTES 


INTERPRETATION    OF    RESULTS    IN    TABLE    Vn  151 

If  proper  compression  has  been  secured  in  trie  construction  of 
a  bituminous  concrete  pavement,  the  percentage  of  voids  as 
above  determined  should  closely  correspond  with  the  voids  in 
a  properly  prepared  laboratory  compressed  sample.  If  a  fine 
aggregate  is  well  graded  and  carries  the  proper  percentage  of 
bituminous  cement,  the  voids  should  be  very  low  and  seldom 
over  3  or  4%. 

INTERPRETATION  OF  RESULTS  IN  TABLE  VXE 

While  it  does  not  come  within  the  scope  of  this  manual  to 
enter  into  an  exhaustive  consideration  of  the  value  of  well- 
grade'd  aggregates  and  the  percentage  of  bitumen  which  they 
should  properly  carry,  a  few  analyses  of  the  more  common  types 
of  bituminous  aggregates  are  given  in  Table  VII,  on  page  152, 
for  the  sake  of  comparison. 

The  sheet  asphalt  topping  shown  in  this  table  is  of  excel- 
lent character  and  carries  normal  proportions  of  bitumen,  filler, 
and  sand.  The  sand  grading  is  also  good.  For  this  type  of 
aggregate  it  has  been  customary  to  adopt  certain  sand  grad- 
ings  as  standard  and  then  in  practice  to  approach  these  stand- 
ards as  closely  as  possible.  Examples  of  two  such  condensed 
standard  gradings  are  as  follows: 

STANDARD  SAND  GRADINGS 


Heavy 

Light 

Traffic 

Traffic 

Passing 

80 

mesh 

and 

retained 

on 

200 

mesh  .... 

34% 

20% 

Passing 

40 

mesh 

and 

retained 

on 

80 

mesh  .... 

43% 

45% 

Passing 

10 

mesh 

and 

retained 

on 

40 

mesh  .... 

23% 

35% 

The  proper  percentage  of  bitumen  and  filler  will  depend  upon 
the  exact  grading.  In  general,  the  finer  the  mineral  aggregate 
the  greater  will  be  the  percentage  of  bitumen  properly  required 
to  bind  and  waterproof  it  after  compression. 

From  the  above  it  will  be  seen  that  the  bituminous  sand- 
stone shows  a  poorly  graded  aggregate  relatively  coarser  than 
the  topping  and  therefore  requiring  less  bitumen.  Such  a  prod- 


152 


ANALYSES    OF    BITUMINOUS    AGGREGATES 


t"*  to 

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I  s 

H  tt 


ll 

CQ1 


Ij 


00  t>-  CO    CM 

\O  >O  00    ON 


vo       co          vo 
vO  CM 


«  ON  IOOO 


vO  CS  CO  to  COOO  O  vO  CO  i-t 

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rt-  n 


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c^"£uS2iu2iv-t-ccc!c 

0000000  o'^'^'^'^ 
O   OOO  lO^fOCN   i-i  Vf  W  M 


—  ccccccccccc 


NOTES 


NOTES 


INTERPRETATION    OF    RESULTS    IN    TABLE    VH  153 

net  after  compression  is  much  more  readily  shoved  and  dis- 
integrated under  traffic  than  is  the  topping,  provided  that  in 
both  cases  the  bitumen  is  of  suitable  consistency. 

The  asphalt  block  is  composed  of  a  compressed  mixture  of 
rock  screenings,  mineral  filler,  such  as  limestone  dust,  and  bitu- 
men. It  is,  in  fact,  a  graded  bituminous  fine  aggregate  concrete. 
A  graded  coarse  aggregate  concrete  would  be  obtained  by  using 
such  a  mix  to  fill  the  voids  in  a  product  such  as  shown  in  the 
last  column. 

The  one-size  broken-stone  concrete  is  composed  of  a  mixture 
of  bitumen  and  one  product  of  a  stone-crushing  and  screening 
plant,  commonly  known  as  commercial  J^-inch  broken  stone. 
It  is  therefore  ungraded.  While  carrying  a  rather  high  percent- 
age of  voids  even  after  compaction  on  the  road,  this  size  stone, 
when  suitably  mixed  with  bitumen,  possesses  sufficient  resist- 
ance to  displacement  to  produce  a  satisfactory  wearing  surface 
under  favorable  conditions. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN     INITIAL     FINE     OF     25     CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


1932 


OCT    6    1934 


JUN   29  1345 


LD  21-50j).-8,-32 


357303 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


